This is the building everyone photographs from the opposite bank of the Arno, a tiny pink-and-white Gothic chapel perched at the river's edge like a marble reliquary. Built between 1230 and 1325, it was originally an oratory at the riverside, but in 1871 it was dismantled and reassembled a metre higher to protect it from flooding. The reconstruction was not entirely faithful and historians still grumble.
The interior is plain by comparison — a single rectangular room — but it sometimes holds small exhibitions, and the play of light through the rose window is worth a minute. Walk past it after dark when the marble glows under uplighting and the river is empty. It is the best small monument in Pisa.