The single greatest monument in Rimini and one of the most important buildings of the early Renaissance. Leon Battista Alberti's white marble facade — modelled on a Roman triumphal arch and intended to wrap a Gothic Franciscan church inside — was begun in the 1450s and remains unfinished, the upper section a stark broken line against the sky.
The interior is a treasure house: Sigismondo Malatesta's tomb, Isotta degli Atti's chapel, a crucifix by Giotto, and a fresco by Piero della Francesca showing Sigismondo himself kneeling before his patron saint. Open most days; admission free.