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 wrote a series of treatises about its supply system. Places that used this commodity were built on top of stacks of pilae (-5[1])tiles. A (-5[1])source of this commodity (15[1])belonging to the Celtic goddess (10[3])(*) Sulis gave its name to a Roman (10[1])town. The Pont du Gard near Nîmes, France was built for this (10[2]-5[1])commodity. A hypocaust heated this (10[2])commodity before use in a (-5[1])caldarium. A city in Somerset, England is named for housing Roman thermae that used this (10[1])commodity.. For 10 points, name this substance that Roman engineers transported with aqueducts. (10[4])■END■