Arezzo's Gothic cathedral sits at the highest point of the old city, surrounded by a small park with views over the Arno valley. Construction began in 1278 and proceeded so slowly that the nave wasn't finished until the early 20th century — the facade was only completed in 1914, in a neo-Gothic style that doesn't quite match the interior.
The interior is one of the better Gothic church spaces in Tuscany: long, relatively dark, with stained glass by Guillaume de Marcillat (a French artist who settled in Arezzo in the early 16th century) flooding the nave with coloured light. The tomb of Pope Gregory X (who died in Arezzo in 1276) is here, as is a glazed terracotta figure by Andrea della Robbia. Free to enter.