In 1867 a Mithraeum was discovered in a notable Roman house, situated under the Basilica S. Clemente. As a continuous flow of water made further investigations impossible in the beginning, the excavations could only be continued in 1914 after the construction of a water-tunnel.
One enters the Mithraeum after descending a number of stairs and passing through a room in front of it. Then come the actual entry (Br. 1.50), which was constructed in later times when the Mithraeum was built. It shows the usual division into a plastered central aisle (Br. 2.