Eric by one of the arcades, looking out over the Arc of Constantine.

The Arc of Constantine itself, as seen from the Colosseum. It was built in 315, and so would have been visible from the Colosseum for the last 200 years or so of its use as an arena.

It's very interesting to be wandering around a building that is clearly very, very old...

... old enough to have water-carved formations in the rock that makes it.

The most striking thing about the Colosseum was the sense of the passage of time, and the contrast between modern, old, and very old...

... a theme that repeats itself throughout Rome.