The Roman Colosseum was huge. The line to get in was even bigger. We were lucky that we went to Palatine Hill before the Colosseum, so we didn’t have to wait in line.
I made a video there: http://www.youtube.com/watch?v=kcLPV9ysMlo
Here are some tips for when you go.
1. Before you go, get tickets in advance. You get to skip the line when you have tickets.
2. See the 7 hills. They are included in the ticket, plus, they are cool to see. You can go to the Circus Maximus, the Forum and visit the old palaces.
3. They have a guided tour that lets you go to the 2nd floor where you can see the trap doors.
4. Bring a camera that zooms WAY out, or, take your pictures from the hill. We made this mistake – it is so big that you have to walk far away to get the whole building in your picture.