Not a nice place to get lost. We were to Sant Agnese, I believe. It is a long time ago, I remember what I saw, sadly, not the names
Well, it was quite funny, we were there from school, like 25 students, 3 professors and their strange friends who didn't care about the art. We got a guide and still 3 people got lost. Our guide was angry and starting to shout something in Italian. After 5 minutes he found the lost ones and continued in guiding. Sadly, there was not much to see. There can be two reason for it. There was really nothing to see, or turists were not allowed to see it. Of course we saw all those graves. People of those times had to be really small and tiny. But still, we also saw one arcosolium
Well, for those who would like to see the graves of first christians and actually the first christian paintings, has to visit catacombs of Saint Callixtus!!! (here's their website with all the information one needs http://www.catacombe.roma.it )
I found a great website about catacombs, here it is: http://www.newadvent.org/cathen/03417b.htm

The Catacombs of Rome are ancient Jewish and Christian underground burial places near Rome, Italy. Etruscans used to bury their dead in underground chambers. Christians revived the practice because they did not want to cremate their dead due to their belief in bodily resurrection. At first they were used both for burial and the memorial services and celebrations of the anniversaries of Christian martyrs. They probably were not used for regular worship. Christian excavators built vast systems of galleries and passages on top of each other. They lie 7-19 meters below the surface in area of more than 2.4 km². Narrow steps that descend as many as four stories join the levels. Passages are about 2.5x1 meters. Burial niches = loculi were carved into walls. They are 40-60 cm high and 120-150 cm long. Some families were able to construct cubicula which would house various loculi and the arquitectural elements of the space would be a support for decoration. Another excellent place for artistic programs were the arcosoliums.

loculi


cubicula


arcosolium