In the 15th century a Mithraeum was discovered on the Piazza S. Silvestro in Capite. About its construction all data fail. The altars and the bases, on which the inscriptions Nos. 400-405, are lost. One inscription (No. 406) however, has been preserved and stands on the back of a marble slab (H. 0.54 Br. 2.25). It was found in 1867 and is divided by small columns into four square and three semicircular niches, in which the seven planets must have been represented.