Piazza Anfiteatro in Lucca

You're standing on Piazza dell'Anfiteatro, in the northeast of Lucca's walled old town. Turn around slowly and take it all in. Notice something odd? This square isn't square at all, and it isn't round either. It's an oval. The houses form a closed ring around you, almost like the stands of an arena. And that's exactly what used to be here.