After seeing that it was one of Tripadvisor's top three most popular sights in Rome, I was also surprised that I couldn't find much about it here. I made a phone reservation in February for my May trip. Be aware that there are only a few English-speaking tour times available. Since I decided I'd buy a Roma Pass when I got to Rome, I called and made my reservations for both the Palazzo Valentini and the Borghese Gallery and was given both confirmation numbers over the phone. After I arrived at our RS tour's hotel in Rome, the front desk clerk called to confirm both reservations. I was even able to buy my Roma Pass at the hotel, and had no problems at check-in (without a ticket or printed confirmation.)
I thought it was really unique and fascinating, and ranks as one of my favorite experiences in Rome. I enjoyed the "high-tech" visual presentation of the ruins as it would have looked in its heyday, but if you prefer the traditional museum setting, it may not suit you. The tour lasts approx. 1-1/2 hours, and includes an informative video on Trajan's column as well. We only had 14 total in our group and were a little confined in some of the areas at times, so that may be the reason for the limited tour size. I recommend reserving as early as possible.
