Emperors with someone else's body

This arch was dedicated to Constantine in 315, three years after he beat his rival Maxentius at the Milvian Bridge. Most of what hangs on it is older than he is.

The eight round medallions come from a monument built for Hadrian, the big rectangular reliefs from an arch of Marcus Aurelius, and the standing figures up top are Dacian prisoners from the time of Trajan. Everything pulled together from at least three emperors who lived a century or two earlier.

The charm is in the heads. On the reused pieces, the faces were chiselled away and recarved so that Constantine came out. If you look closely, you'll see those heads don't quite fit their bodies: they're smaller, smoother, and clearly from another hand.

The newly made parts, the narrow friezes just above the side arches, give away where craftsmanship stood in the fourth century. The figures are flat, squat, and all the same size.

We walk east along the street behind the Colosseum until we reach the sunken ground with the half oval.