Long thought to have been a tomb, this round structure has been shown by P. Pensabene and A. Ottati ("Architettura dorica a Villa Adriana," Lazio e Sabina 6 [2010] 23-38) to have been a belvedere in the form of a round tholos in the Doric order with ten columns of Pentelic marble. The trabeation was mixed Ionic-Doric. The "Mausoleum" was thus the pendant of Roccabruna on the other side of the villa. The building can be dated on the basis of a brick stamp to after 123 CE.