We plan to visit the Catacombs of San Callisto on a Sunday in May. I read that traffic is restricted on the Appian Way on Sundays. Is it still possible to take a taxi to this area on Sundays? Also, if we take bus 118 where does it originate in Rome?
I don't know the exact answer to your question, but it might be in here at Ron in Rome's excellent site: http://www.roninrome.com/%20sites-and-attractions/the-catacombs-of-rome
Taxis and buses are permitted. You can take the metro to the Colli Albani stop and then bus 660. Not familiar with bus 118. Also the Archeobus hop on/off is easy to use.
We took the bus on a Sunday going out there to the catacombs. That worked fine. However, the return trip wasn't as easy with the reduced bus schedule as we waited a full hour before our bus arrived. Mind you, we saw at least two busses going the opposite direction during that time period ... We definitely wished we would have taken a taxi back to our hotel. Can't remember which bus line we took. I do remember that we took the metro to Circo Massimo and then the bus from there.