The Decennium is a vast plain outside the Aurelian Wall, south of the Cælius and east of the Aventine. A small brook flows through it, the l'Aqua Craba , that supplies the water to the aqueduct Aqua Damnata, and ends up into the Tiber, passing under the Circus Maximus; the aqueduct, which went over the Via Appia, had a bad reputation as to the quality of its water. By the Porta Metrovia the river got canalised into an underground main (down left on the picture) down to the Tiber.

Here is the Decennium, but a little more eastwards. Several buildings follow the bends of the Aqua Craba, but also many tombs and altars. The Via Asinaria and the Via Tusculana go over the Aqua Craba and lead to the Cælius, top left, and to the Esquiline, top right of the picture.