Pilae (singular ''pila'') is the Latin word the ancient Romans used for "piers", "piles" or "pylons", vertical pillars often used to support structures such as

hypocaust A hypocaust () is a system of central heating in a building that produces and circulates hot air below the floor of a room, and may also warm the walls with a series of pipes through which the hot air passes. This air can warm the upper floors a ...

s. Pilae were also used in

concrete Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...

piers in the Gulf of Pozzuoli at Baiae, Misenum, and Nisida. These are illustrated in a 1st-century fresco from

Stabiae Stabiae () was an ancient city situated near the modern town of Castellammare di Stabia and approximately 4.5 km (2.79 miles) southwest of Pompeii. Like Pompeii, and being only from Mount Vesuvius, it was largely buried by tephra ash in ...

. Ancient glass flasks have been found that illustrate the Puteoli breakwaters with the inscription "pilae".Livy, History 40.51.4: pilas pontis in Tiberi

References

{{reflist Ancient Roman architectural elements