Down a quiet side street, behind a plain stone facade, this small confraternity chapel hides one of the great fresco cycles of late medieval Italy. The Salimbeni brothers of San Severino painted every wall in 1416 — the Life of John the Baptist on the side walls and a vast Crucifixion covering the apse.
The detail is extraordinary: dogs, falcons, donors in fashionable robes, and a Calvary scene crammed with mourners and soldiers in vivid blues, reds and gold. There's a small admission fee, often combined with the neighbouring Oratorio di San Giuseppe (which holds a remarkable terracotta nativity scene). Hours are short; check before climbing the hill.