Helena's Mausoleum is a funerary monument of the Roman age along the Via Casilina. It was built by the Emperor Constantine in 326 and 330, originally intended to serve as a burial for himself, then used as a tomb for Helena, Emperor's mother, who died in 328. The area on which stands the Mausoleum is part a complex of historic buildings late imperial and a previous necropolis. The Mausoleum is one of the most important architectural complexes of the early Christian Rome of the fourth century. The building has a circular plant, constituted by two overlapping cylinders, of which the upper smaller in diameter, with a dome. To lighten the weight of the dome have been included in the construction some empty amphorae (called pignatte) visible today due to the collapse of the vault. In the rectangular niche opposite the entrance there was the sarcophagus of red porphyry, decorated with scenes of war (which feeds the idea that it was initially intended to accommodate Constantine). Between 1993 and 2000, the Mausoleum has undergone major restoration, with the demolition of the additions made in later times and the construction of two balconies on the first and second floor, to enable the view.