In Ancient Rome, the Aqua Alsietina (sometimes called Aqua Augusta) was the earlier of the two western Roman aqueducts (with the aqua Traiana), erected sometime around 2 BC, during the reign of emperor Augustus. It was the only water supply for the Transtiberine region, on the right bank of the river Tiber. This water was not suitable for drinking, however, and Augustus used it to fill his naumachia in Trastevere. This water supply allowed the public to enjoy sham naval battles. The water surplus was used for the irrigation of Caesar's horti (gardens) and for the irrigation of fields.