Our first major stop in Rome was the Colosseum. On a tip from a Rick Steve's Guide to buy tickets at the Forum entrance, we avoided lines and strolled the Forum ruins before entering. The view was remarkable and the late afternoon sunlight hit the Colosseum at various dramatic angles. We took our time and circumnavigated both levels, quietly imagining what a roaring crowd would have sounded like 2,000 years ago. It's crowded for a reason, because it's nothing less than awesome. If you are interested in the structure and history, I recommend the Khan Academy Smart History videos.