The Colosseum needs no introduction. When people talk about Rome and ancient architecture in general, this will immediately come to mind. After all the centuries of wear and tear, it’s still one of the most impressive ruins out there. I wish I had more time to explore inside (*you* try walking from Vatican City to here and back and dealing with the huge lines in a single afternoon!), but I’m so glad I finally got to see it. A larger version is viewable here.
Polymathically 