Several facilities for supplying this commodity in Roman Italy were built at Subiaco. The Anio Vetus was a poor quality source of this commodity compared to the Anio Novus. After being appointed as a curator named for this commodity, Frontinus (15[1])wrote a series of treatises about its supply (15[1])system. This commodity was used in chambers built on top of stacks of pilae tiles. A source of this commodity belonging to the Celtic goddess (*) Sulis gave its name to a (10[1])Roman (10[1])town. The Pont du Gard near (10[1]-5[1])Nîmes, France was built for this (10[1])commodity. A (10[1])hypocaust heated this (10[2])commodity before use in a caldarium. A city in Somerset, England is named for housing Roman thermae that used this commodity. For 10 points, name this substance that Roman engineers transported with aqueducts. (10[1])■END■