Catacombs in Rome

The catacombs cannot be visited without a guide, and there are guides available onsite. I suggest you ask what a private tour offers that the onsite guide does not (more detail, access to parts of the site that onsite guides don't cover, more time). Some of the onsite guides are excellent, some others seem to rush through. I would think thaa private company would be more consistent in what they offer.

Thanks, Zoe. Are they worth seeing? I am having trouble deciding out of the many things to do in 6 days.

Zoe, Walks of Italy does a tour of the other catacombs - the capuchin monks, Priscilla, etc. I think this is the one mbheart is asking about.

Are they worth seeing?

Answers to the 'worth' question are always subjective as what might be of value to one may not be to another. Should you decide to do one - and I think one is enough unless you have a deep interest in them - you can do it without pre-booking a tour. To my knowledge, virtually all of them involve access only with a guide, and guides are available at the sites (although I haven't researched ALL of them).

We did San Sebastiano on the Appia Antica as one of the many attractions available along our long and thoroughly enjoyable walk on the ancient road: our #1 "best thing" in Rome so far, and a great day we'll do again. It was just a matter of stopping in and buying a ticket for a tour in our language. There was a bit too much religion in the guide's narrative (believe what you will) but was it worth it? Yes. The history, mix of tomb types, decoration and uses (this one had a banqueting room) of this subterranean cemetery was interesting. Tickets were about 8 euros; proper dress is required (covered knees and shoulders); photography is not allowed; bring a small flashlight for peering down unlit side tunnels. Remains which had not been cremated (per pre-Christian, Roman custom) have been removed from open niches and relocated so this isn't a 'bone' experience.

http://www.catacombe.org/uk_index.html

I have visited all of the major catacombs, my favorite is the Catacombs of Priscilla, easy to reach by bus on Via Nomentana. A few interesting churches are nearby as well. I used the onsite guide, who was very good.