Pl.: alvei

A hot-water pool, mainly found in the heated rooms of Roman-style baths. Most of these pools could accommodate several people at a time. The hot water was supplied by a boiler in the service rooms, mounted above the furnace of the hypocaust. It was kept warm by means of the hypocaust running under the pool and/or by means of a testudo. Alternatively, the alveus was heated only by an underlying furnace or by the hypocaust and wall heating.

One of the alvei of the caldarium of the Forum Baths of Ostia (room H on this plan). Note the two small square openings in the back wall, presumably for the water supply to the pool, and the larger one underneath for the furnace and probably a testudo alvei (photo Allison Smith).