Silistra ( ; ; or ) is a town in
Northeastern Bulgaria
Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is situated on the eastern portion of the Balkans directly south of the Danube river and west of the Black Sea. Bulgaria is bordered by Greece and Turkey t ...
. The town lies on the southern bank of the lower
Danube
The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...
river, and is also the part of the
Romania
Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
n
border
Borders are generally defined as geography, geographical boundaries, imposed either by features such as oceans and terrain, or by polity, political entities such as governments, sovereign states, federated states, and other administrative divisio ...
where it stops following the Danube. Silistra is the administrative center of the
Silistra Province and one of the important towns of the historical region of
Dobruja
Dobruja or Dobrudja (; or ''Dobrudža''; , or ; ; Dobrujan Tatar: ''Tomrîğa''; Ukrainian language, Ukrainian and ) is a Geography, geographical and historical region in Southeastern Europe that has been divided since the 19th century betw ...
.
Silistra is a major cultural, industrial, transportation, and educational center of Northeastern Bulgaria. There are many historical landmarks including a
richly-decorated Late Roman tomb, remains of the medieval fortress, an
Ottoman fort, and an art gallery.
Etymology
The name Silistra is possibly derived from the root of the old
Thracian
The Thracians (; ; ) were an Indo-European speaking people who inhabited large parts of Southeast Europe in ancient history.. "The Thracians were an Indo-European people who occupied the area that today is shared between north-eastern Greece, ...
name of the lower part of the
Danube
The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...
"
Istrum".
The name of the city is given as ''Silistria'' in the
''Encyclopædia Britannica'' Eleventh Edition.
Geography
Silistra is in the northeastern part of Bulgaria on the southern bank of the
Danube
The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...
River. It is located in the Bulgarian part of
Dobruja
Dobruja or Dobrudja (; or ''Dobrudža''; , or ; ; Dobrujan Tatar: ''Tomrîğa''; Ukrainian language, Ukrainian and ) is a Geography, geographical and historical region in Southeastern Europe that has been divided since the 19th century betw ...
.
The
municipality of Silistra covers an area of 516 km
2 and includes the town and 18 villages. The area of the city proper is 27.159 km
2.
Silistra is 431 km from Sofia, the capital of Bulgaria; 141 km from Varna; and 119 km from Ruse.
Climate
Silistra has a
temperate climate
In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ra ...
, with cold snowy winters and hot summers.
History

After the Roman province of
Moesia
Moesia (; Latin: ''Moesia''; ) was an ancient region and later Roman province situated in the Balkans south of the Danube River. As a Roman domain Moesia was administered at first by the governor of Noricum as 'Civitates of Moesia and Triballi ...
was founded in 12 AD, the
Romans built a fort in 29 on the site of an earlier
Thracian
The Thracians (; ; ) were an Indo-European speaking people who inhabited large parts of Southeast Europe in ancient history.. "The Thracians were an Indo-European people who occupied the area that today is shared between north-eastern Greece, ...
settlement and kept its name, ''Durostorum'' (or ''Dorostorum''). During the reigns of
Claudius
Tiberius Claudius Caesar Augustus Germanicus ( ; ; 1 August 10 BC – 13 October AD 54), or Claudius, was a Roman emperor, ruling from AD 41 to 54. A member of the Julio-Claudian dynasty, Claudius was born to Nero Claudius Drusus, Drusus and Ant ...
(41-54 AD) and Nero (54-68), the eastern border of Moesia was extended to the mouth of the river Iatrus (the modern Yantra). Durostorum was one of several important river points along the
Moesian Limes frontier. After
Trajan's Dacian Wars
Trajan's Dacian Wars (101–102, 105–106) were two military campaigns fought between the Roman Empire and Dacia during Roman Emperor, Emperor Trajan's rule. The conflicts were triggered by the constant Dacian threat on the Danube, Danubian Rom ...
the fort was enlarged into a legionary fortress for the
Legio XI Claudia
Legio XI Claudia ("Claudius' Eleventh Legion") was a legion of the Imperial Roman army. The legion was levied by Julius Caesar for his campaign against the Nervii. XI ''Claudia'' dates back to the two legions (the other was the XIIth) recruit ...
who stayed there from before 114 until c. 400. It became an important military centre of the Roman province of
Moesia
Moesia (; Latin: ''Moesia''; ) was an ancient region and later Roman province situated in the Balkans south of the Danube River. As a Roman domain Moesia was administered at first by the governor of Noricum as 'Civitates of Moesia and Triballi ...
, and grew into a city at the time of
Marcus Aurelius
Marcus Aurelius Antoninus ( ; ; 26 April 121 – 17 March 180) was Roman emperor from 161 to 180 and a Stoicism, Stoic philosopher. He was a member of the Nerva–Antonine dynasty, the last of the rulers later known as the Five Good Emperors ...
. The city was strongly affected by an invasion of the
Costoboci
The Costoboci (; , or Κιστοβῶκοι) were a Dacian tribe located, during the Roman imperial era, between the Carpathian Mountains and the river Dniester river, Dniester. During the Marcomannic Wars the Costoboci invaded the Roman Empire i ...
in 170.
Large thermal baths have been discovered in the ''canabae'' and residential buildings to the south. There were six periods of construction between the 2nd and 4th centuries AD.
When the Roman Empire split into the
Eastern and
Western empire
In modern historiography, the Western Roman Empire was the western provinces of the Roman Empire, collectively, during any period in which they were administered separately from the eastern provinces by a separate, independent imperial court. ...
s, the town became part of the Eastern Roman Empire.
Durostorum became the seat of a Christian bishopric and a centre of Christianity in the region. The earliest saints of Bulgaria are Roman soldiers executed at Durostorum during the
Diocletian Persecution (303–313), including
St. Dasius and
St. Julius the Veteran.
Auxentius was expelled from Durostorum by an edict of Theodosius depriving Arian bishops in 383, and took refuge at Milan where he became embroiled in controversy with St
Ambrose
Ambrose of Milan (; 4 April 397), venerated as Saint Ambrose, was a theologian and statesman who served as Bishop of Milan from 374 to 397. He expressed himself prominently as a public figure, fiercely promoting Roman Christianity against Ari ...
. The Roman general
Flavius Aëtius was born in the town in 396.
As part of the
Bulgarian Empire Bulgarian Empire may refer to:
* First Bulgarian Empire
The First Bulgarian Empire (; was a medieval state that existed in Southeastern Europe between the 7th and 11th centuries AD. It was founded in 680–681 after part of the Bulgars, led b ...
Durostolon was known as ''Drastar'' in medieval times.

Around the end of the 7th century, the town was incorporated into the
First Bulgarian Empire
The First Bulgarian Empire (; was a medieval state that existed in Southeastern Europe between the 7th and 11th centuries AD. It was founded in 680–681 after part of the Bulgars, led by Asparuh of Bulgaria, Asparuh, moved south to the northe ...
and the bishop of ( in Bulgarian) was proclaimed the first
patriarch of Bulgaria
The Patriarch of All Bulgaria () is the patriarch of the Bulgarian Orthodox Church. The patriarch is officially styled as ''Patriarch of All Bulgaria and Metropolitan of :bg:Софийска епархия, Sofia''. The current patriarch Daniil of ...
. In 895 (during the
Bulgarian-Hungarian War of 894–896), the Hungarians, allies of the Byzantines, besieged the Bulgarian army under the personal command of
Simeon I the Great in the fortress of the town but were repulsed. The next year the Hungarians were decisively defeated in the
battle of Southern Buh.
The town
was captured by the forces of
Sviatoslav I of Kiev in 969, but two years later it was taken by the Byzantines during the
Battle of Dorostolon. In 976, Tsar
Samuel
Samuel is a figure who, in the narratives of the Hebrew Bible, plays a key role in the transition from the biblical judges to the United Kingdom of Israel under Saul, and again in the monarchy's transition from Saul to David. He is venera ...
restored Bulgarian rule in the region until 1001, when it once again became part of the Byzantine Empire as ''Dristra''. Emperor
Alexios I Komnenos
Alexios I Komnenos (, – 15 August 1118), Latinization of names, Latinized as Alexius I Comnenus, was Byzantine Emperor, Byzantine emperor from 1081 to 1118. After usurper, usurping the throne, he was faced with a collapsing empire and ...
suffered a defeat at Dristra to the
Pechenegs
The Pechenegs () or Patzinaks, , Middle Turkic languages, Middle Turkic: , , , , , , ka, პაჭანიკი, , , ; sh-Latn-Cyrl, Pečenezi, separator=/, Печенези, also known as Pecheneg Turks were a semi-nomadic Turkic peopl ...
in 1087.
In 1186, after the
Rebellion of Asen and Peter, the town became part of the Second
Bulgarian Empire Bulgarian Empire may refer to:
* First Bulgarian Empire
The First Bulgarian Empire (; was a medieval state that existed in Southeastern Europe between the 7th and 11th centuries AD. It was founded in 680–681 after part of the Bulgars, led b ...
and renamed Drastar.
In 1279, under Emperor
Ivailo, Drastar was attacked by the
Mongols
Mongols are an East Asian ethnic group native to Mongolia, China ( Inner Mongolia and other 11 autonomous territories), as well as the republics of Buryatia and Kalmykia in Russia. The Mongols are the principal member of the large family o ...
; but after a three-month-long siege the Bulgarians managed to break through. The town remained part of the Bulgarian Empire until the
Ottoman conquest of the Balkans
A series of military conflicts between the Ottoman Empire and various European states took place from the Late Middle Ages up through the early 20th century. The earliest conflicts began during the Byzantine–Ottoman wars, waged in Anatolia i ...
around 1400. Throughout the Middle Ages, Drastar (possibly known by the name Silistra too) was among Bulgaria's largest and most important cities.
During
Ottoman rule, Silistra (
Ottoman Turkish
Ottoman Turkish (, ; ) was the standardized register of the Turkish language in the Ottoman Empire (14th to 20th centuries CE). It borrowed extensively, in all aspects, from Arabic and Persian. It was written in the Ottoman Turkish alphabet. ...
: ) was part of
Rumelia Province and was the administrative centre of the Silistra district (''
sanjak
A sanjak or sancak (, , "flag, banner") was an administrative division of the Ottoman Empire. The Ottomans also sometimes called the sanjak a liva (, ) from the name's calque in Arabic and Persian.
Banners were a common organization of nomad ...
''). This district was later upgraded to become the
Silistra Province and stretched over most of the western
Black Sea
The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...
littoral
The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely i ...
. In 1570 (
Hijri 977) the town of Silistra was inhabited by Muslims and Christians. It had 447 Muslim households in 20 neighbourhoods and 633 Non-muslim households in 15 neighbourhoods. The defter also recorded that there was a Jewish and a Christian Romani congregation.
The town was captured and recaptured by
Russian forces numerous times during several
Russo-Turkish Wars
The Russo-Turkish wars ( ), or the Russo-Ottoman wars (), began in 1568 and continued intermittently until 1918. They consisted of twelve conflicts in total, making them one of the longest series of wars in the history of Europe. All but four of ...
and was besieged between 14 April and 23 June 1854 during the
Crimean War
The Crimean War was fought between the Russian Empire and an alliance of the Ottoman Empire, the Second French Empire, the United Kingdom of Great Britain and Ireland, and the Kingdom of Sardinia (1720–1861), Kingdom of Sardinia-Piedmont fro ...
.
Namık Kemal wrote his most famous play, ''
Vatan Yahut Silistre'' ("Homeland or Silistre"), a drama about the
siege of Silistra (''Silistria''), in which he expounded on the ideas of patriotism and liberalism. The play was first staged on 1 April 1873 and led to his exile to
Famagusta
Famagusta, also known by several other names, is a city located on the eastern coast of Cyprus. It is located east of the capital, Nicosia, and possesses the deepest harbour of the island. During the Middle Ages (especially under the maritime ...
.
The Ottoman Silistra Province was reduced in size, as the districts of
Özi and
Hocabey and the region of
Bessarabia
Bessarabia () is a historical region in Eastern Europe, bounded by the Dniester river on the east and the Prut river on the west. About two thirds of Bessarabia lies within modern-day Moldova, with the Budjak region covering the southern coa ...
were ceded to the Russian Empire at the end of the 18th century and the beginning of the 19th century. Edirne Province was created from its southern regions in 1830. Finally, Silistra Province merged with the provinces of
Vidin
Vidin (, ) is a port city on the southern bank of the Danube in north-western Bulgaria. It is close to the borders with Romania and Serbia, and is also the administrative centre of Vidin Province, as well as of the Metropolitan of Vidin (since ...
and
Niš
Niš (; sr-Cyrl, Ниш, ; names of European cities in different languages (M–P)#N, names in other languages), less often spelled in English as Nish, is the list of cities in Serbia, third largest city in Serbia and the administrative cente ...
in 1864 to form
Danube Province. Silistra was downgraded to a ''kaza'' centre in
Ruse district in this province in the same year.
Between 1819 and 1826,
Eliezer Papo — a renowned
Jew
Jews (, , ), or the Jewish people, are an ethnoreligious group and nation, originating from the Israelites of ancient Israel and Judah. They also traditionally adhere to Judaism. Jewish ethnicity, religion, and community are highly inte ...
ish scholar — was the
rabbi
A rabbi (; ) is a spiritual leader or religious teacher in Judaism. One becomes a rabbi by being ordained by another rabbi—known as ''semikha''—following a course of study of Jewish history and texts such as the Talmud. The basic form of t ...
of the community of Silistra, making this town famous among observant Jews. Up to the present, his grave is a focus of
pilgrimage
A pilgrimage is a travel, journey to a holy place, which can lead to a personal transformation, after which the pilgrim returns to their daily life. A pilgrim (from the Latin ''peregrinus'') is a traveler (literally one who has come from afar) w ...
, some pilgrims flying from
Israel
Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
and even from
Latin America
Latin America is the cultural region of the Americas where Romance languages are predominantly spoken, primarily Spanish language, Spanish and Portuguese language, Portuguese. Latin America is defined according to cultural identity, not geogr ...
to Bulgaria for that purpose.
In 1878, following the
Russo-Turkish War of 1877–1878, Silistra was included in Bulgaria.
Romania
Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
was opposed to this as it wanted to acquire the city and established the short-lived
Silistra Nouă County
Silistra Nouă County was a county ('' județ'') of Romania, in Northern Dobruja, with its capital city first at Rasova, later at Cernavodă and finally at Medgidia. It was established on 13 November 1878 and abolished on 1 April 1879. After ...
, which was abolished a year later.
In May 1913, following the
Second Balkan War
The Second Balkan War was a conflict that broke out when Kingdom of Bulgaria, Bulgaria, dissatisfied with its share of the spoils of the First Balkan War, attacked its former allies, Kingdom of Serbia, Serbia and Kingdom of Greece, Greece, on 1 ...
and after unsuccessful Bulgarian-Romanian negotiations in
London
London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
, the two countries accepted the mediation of the
Great Powers, who awarded Silistra and the area in a 3 km radius around it to Romania at the
Saint Petersburg
Saint Petersburg, formerly known as Petrograd and later Leningrad, is the List of cities and towns in Russia by population, second-largest city in Russia after Moscow. It is situated on the Neva, River Neva, at the head of the Gulf of Finland ...
Conference. The 1913
Treaty of Bucharest ceded Silistra and the whole of
Southern Dobruja
Southern Dobruja or South Dobruja ( or simply , ; or , ), also the Quadrilateral (), is an area of north-eastern Bulgaria comprising Dobrich and Silistra provinces, part of the historical region of Dobruja. It has an area of 7,412 square km an ...
to
Romania
Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
. Bulgaria regained the town from 1916 during
World War I
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
. This became finalised with the
Treaty of Bucharest in 1918 after Romania surrendered to the
Central Powers
The Central Powers, also known as the Central Empires,; ; , ; were one of the two main coalitions that fought in World War I (1914–1918). It consisted of the German Empire, Austria-Hungary, the Ottoman Empire, and the Kingdom of Bulga ...
(of which Bulgaria was a part). The
Treaty of Neuilly (1919) following
World War I
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
returned it to Romania. Silistra remained a part of Romania until the
Axis
An axis (: axes) may refer to:
Mathematics
*A specific line (often a directed line) that plays an important role in some contexts. In particular:
** Coordinate axis of a coordinate system
*** ''x''-axis, ''y''-axis, ''z''-axis, common names ...
-sponsored
Treaty of Craiova
The Treaty of Craiova (; ) was signed on 7 September 1940 and ratified on 13 September 1940 by the Kingdom of Bulgaria and the Kingdom of Romania. Under its terms, Romania had to allow Bulgaria to retake Southern Dobruja, which Romania had gained ...
in 1940, when the town once again became part of Bulgaria, a transfer confirmed by the
Paris Peace Treaties in 1947. Between 1913 and 1938, Silistra was the capital of
Durostor County (except during Bulgarian rule). It became part of
Ținutul Mării
Ținutul Mării (alternatively spelled as ''Marea'' or ''Mărei'') was one of the ten ''ținuturi'' ("lands") of Romania, founded in 1938 after King Carol II initiated an institutional reform by modifying the 1923 Constitution and the law of terri ...
("Sea District") between 1938 and 1940 during Romanian rule. Following the establishment of the People's Republic of Bulgaria, Silistra developed as a center of industry and agriculture in the region, comparable to Ruse (because of the strategic position on the Danube) and Dobrich (due to the abundant fertile lands). This led to a major population increase which continued until 1985. After that, the population slowly started to decrease. Following the collapse of the People's Republic in 1989, many of its inhabitants migrated to other parts of the country or emigrated outside Bulgaria.
Population
In January 2012, Silistra was inhabited by 35,230 people within the city limits, while the
Silistra Municipality along with the legally affiliated adjacent villages had 50,780 inhabitants.
[National Statistical Institute - 2012]
The number of the residents of the city (not the municipality) reached its peak in the period 1986–1991, when it exceeded 70,000.
The following table presents the change of the population after 1887.
Ethnic, linguistic and religious composition
According to the latest 2011 census data, the individuals declared their ethnic identity were distributed as follows:
Population by province, municipality, settlement and ethnic identification, by 01.02.2011; Bulgarian National Statistical Institute
*Bulgarians
Bulgarians (, ) are a nation and South Slavs, South Slavic ethnic group native to Bulgaria and its neighbouring region, who share a common Bulgarian ancestry, culture, history and language. They form the majority of the population in Bulgaria, ...
: 29,677 (88.3%)
* Turks: 3,458 (10.3%)
* Romani: 123 (0.4%)
*Others: 190 (0.6%)
*Indefinable: 180 (0.5%)
**Undeclared: 1,979 (5.6%)
Total: 35,607
Notable people
* Flavius Aetius
Flavius Aetius (also spelled Aëtius; ; 390 – 21 September 454) was a Roman Empire, Roman general and statesman of the Fall of the Western Roman Empire, closing period of the Western Roman Empire. He was a military commander and the most inf ...
(396–454), a Roman general, defeated Attila the Hun
Attila ( or ; ), frequently called Attila the Hun, was the ruler of the Huns from 434 until his death in early 453. He was also the leader of an empire consisting of Huns, Ostrogoths, Alans, and Gepids, among others, in Central and East ...
* Parteniy Pavlovich (c. 1695 – 1760), cleric, author of the first autobiography in South Slavic literature
* Orfi (1943–1999), magician
* Yıldız İbrahimova (1952–), jazz singer
* Veselin Metodiev (1957–), former minister of culture
* Denislav Kalchev (1973–), swimmer
Twin towns – sister cities
Silistra is twinned with:
* Veles, North Macedonia
* Dunaújváros
Dunaújváros (; also known by #Etymology and names, alternative names) is an industrial city in Fejér County, Central Hungary. It is a city with county rights. Situated 70 kilometres (43 miles) south of Budapest on the Danube, the city is best ...
, Hungary
* Dresden
Dresden (; ; Upper Saxon German, Upper Saxon: ''Dräsdn''; , ) is the capital city of the States of Germany, German state of Saxony and its second most populous city after Leipzig. It is the List of cities in Germany by population, 12th most p ...
, Germany
* Leskovac
Leskovac ( sr-Cyrl, Лесковац, ) is a List of cities in Serbia, city and the administrative center of the Jablanica District in Southern Serbia (Geographical Region), southern Serbia. According to the 2022 census, the city itself has a p ...
, Serbia
* Lüleburgaz, Turkey
* Slobozia, Romania
* Lida
Lida is a city in Grodno Region, western Belarus, located west of Minsk. It serves as the administrative center of Lida District. As of 2025, it has a population of 103,262.
Etymology
The name ''Lida'' arises from its Lithuanian name ''Ly ...
, Belarus
* Óbuda-Békásmegyer
Óbuda-Békásmegyer is the List of districts in Budapest, 3rd district of Budapest, Hungary.
Landmarks
* Aquincum, ruins of the Roman city
* Óbuda Jewish Cemetery
* Római Part (Roman Beach)
History
The military camp, then city of Aquincum, l ...
, Hungary
Honour
Silistra Knoll on Livingston Island
Livingston Island (Russian name ''Smolensk'', ) is an Antarctic island in the Southern Ocean, part of the South Shetland Islands, South Shetlands Archipelago, a group of List of Antarctic and subantarctic islands, Antarctic islands north of the ...
in the South Shetland Islands
The South Shetland Islands are a group of List of Antarctic and subantarctic islands, Antarctic islands located in the Drake Passage with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the n ...
, Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
is named after Silistra.
"Silistra" is also the name of a fictional planet in Janet Morris' book '' High Couch of Silistra'' (1977).
References
External links
Official municipality website
(in Bulgarian and English)
News from UNESCO nature reserve in Silistra
Awarded "EDEN - European Destinations of Excellence" non traditional tourist destination 2010
{{Authority control
Populated places in Silistra Province
Port cities and towns in Bulgaria
Populated places on the Danube
Bulgaria–Romania border crossings
Jewish pilgrimage sites
Capitals of former Romanian counties
Roman legionary fortresses in Bulgaria
Roman towns and cities in Bulgaria