In the sacristy hangs a painting of the Immaculate conception with angels by Giovanni Odazzi, and on the main altar a Baptism of Santa Prisca by Domenico Passignano.

[1] This had also served as Trajan's town house until his death in 117 A.D. One hundred years later, a member of the imperial family took over the building and built a Mithraeum in one part of the basement, while a Christian meeting place was established in the other section.

Renovations in 220[citation needed] yielded a larger central cult room and the addition of new ones while the frescoes were covered with new, more elaborate paintings.

For example, one painting shows a procession of figures wearing masks and different colored tunics holding what has been presumed to be a piece of liturgical equipment.

The Mithraeum had been embellished with paintings, and these frescoes, in particular, contain imagery and iconography which depict particular beliefs in the Mithraic cult as well as elements of initiation.

[3] Both the left and right walls in the Mithraeum of Santa Prisca have remnants of paintings which depict different scenes and include several figures; however, due to destruction, some of the images are difficult to make out.

[1] Another figure in the painting is seen standing, wearing a red tunic and is depicted with a raven face mask and proffering an oblong dish.

The right wall fresco in the Mithraeum features the seven grades arranged in the exact order (followed by their symbols): The Dutch excavations of M. J. Vermaseren and C. C. Essen in the mid 20th century also revealed there to be paintings in the temples underneath the church.

[1] The findings of Vermaseren and Essen also found there to be similarities to another Mithreaum in Ostia Antica, a harbor city 19 miles (30 kilometers) from Rome.