<p>An aqueduct built by Augustus (and sometimes called <i>aqua Augusta</i>, according to Frontinus) mainly to supply the *Naumachia of 2 B.C. (Evans), but also used for irrigation of private estates in the *Trans Tiberim and during emergencies when other lines supplying the area were cut off (Frontin., <i>Aq</i>. 11.1-2). Only a small portion of the canal survives, discovered in 1926 on the *Ianiculum near Viale XXX Aprile (cf. Taylor 487, fig. 7). The Alsietina is also represented on the Severan Marble Plan (Rodríguez Almeida, <i>Forma</i> pl. 30, frag. 37B), but the precise location of these fragments is unclear (cf. Taylor 478, fig. 4). On the map the course of the Alsietina has been reconstructed mainly on the basis of Frontinus’ account (<i>Aq</i>. 11.1-3, 22.4, 85), which indicates that the Alsietina approached the city from the W, dropping sharply from the ridge of the Ianiculum to a terminal point behind the Naumachia (cf. Liberati Silverio).</p>