You can't leave Rome (the 2nd time) without appreciating its graffiti. Most of the high quality drawing is either far from the center or safely viewable only from moving trains or with gang member friends as guides. We found a very good, very dependable, and reasonably accessible site. From the Baths of Caracalla, follow via di Porta San Sebastiano (this is an old Roman road, high walls, no sidewalks, fast moving one-way traffic - but people do walk it [we have]) south, about half mile through the wall and gate and just beyond, to the underpass created by via Cilicia. You can't miss the art work here on the beginning of via Appia Antica, but we especially recommend the display of talent as one moves left and under the nearby exit off via Cilicia. Poke around. Really quite something.