Booking will soon start for the night underground tour of the colosseum. This is considered a special event so does not include entry to the forum/palatine hill. This is a full guided tour of the colosseum including the underground areas. You will not be allowed to explore on your own during this tour. The upper levels are not available for this tour.
https://www.coopculture.it/en/events.cfm?id=177
The night tour is a great way to extend your touring time for Rome.
Donna