This jewel of Rome's history is a must-see for the history enthusiast. Entering at street level, you see a 12th century church. Descending the stairs, you find a 4th century church and below that is the first century Temple of Mithras. Definitely not the typical Italian church filled with art and mosaics. The atmosphere is dark and gloomy, but the opportunity to see these surviving layers of Rome's past are memorable.