The vast plain brick basilica of the Dominicans, on a ridge west of the centre, with one of the best views back across the city to the Duomo. The interior is austere — a single barn-like nave — but holds Andrea Vanni's 14th-century portrait of Catherine of Siena, made during her lifetime and the only contemporary image of the saint.
The Chapel of Saint Catherine has frescoes by Sodoma showing her ecstasies. A glass reliquary holds her preserved head. She was canonised in 1461.