The dome that isn't

From the outside, Sant'Ignazio is an ordinary baroque church front on a small square, and the square itself is already a kind of theatre. The architect designed the surrounding houses like stage wings, with facades that curve inward as if someone might step out onto them at any moment, giving the church the set for its own performance.

What lies behind it is stranger still. Above the nave hangs a dome made of paint, because the money for a real one ran out and the neighbours complained that it would steal their light. Andrea Pozzo, a Jesuit painter and master of perspective, solved the problem at the end of the seventeenth century with a painted canvas seventeen metres across, and it only works from a single point on the floor.

The church is free and closes for a couple of hours around midday. Inside you'll find the second half of this stop, which leads you to that one point and shows you what happens when you step beside it.