This vast and peculiar building was already the 200-year old church and burial-place of the Malatesta family, rulers of Rimini, when their most glorious but ill-fated son, Sigismondo Pandolfo, hired Leon Battista Alberti in 1451 to design new, classical facades to cover its Gothic walls, and extend it with a vast dome (never started, but intended to rival the Pantheon in Rome.) Malatesta, a hugely successful Condottiero, or mercenary general, conceived the building as a monumental sepulchre for his family and his mistress, and later wife, Isotta degli Atti. The work was hampered by Malatesta's declining fortunes, and halted completely by his death in 1468, leaving it with broken, unfinished facades.

The interior houses a famous fresco by Piero della Francesca, of Sigismondo kneeling before St Sigismund; otherwise there is almost no Christian imagery. Instead there are vast monuments to the glory of his and Isotta's families, framed by fantastical confections of exquisite carving by Agostino di Duccio. The project's pagan imagery was used by Malatesta's great enemy, Pope Pius II Piccolomini, along with a battery of slanders (incest, murder of his wives, sodomy of his sons) to justify his excommunication. 

Agostino's cherubs in the reliefs of the 'Chapel of Childhood Games' have a strange, slightly threatening air; mixed with them are elephants, an important emblem for Malatesta, which appear throughout.

There are stylised heraldic elephant crests in a Rosso Verona marble railing and atop a grand tomb, its sarcophagus held by more elephants, while pairs of black marble ones (oddly Dumbo-like) hold up tiered carvings framing one chapel. Parts of the church have been altered and moved around over the centuries, leaving evocative empty spaces and mysterious, isolated pieces of carving. The church reclaimed the space after the 'heretic' Malatesta's death, and it is now the Cathedral of Rimini, but its heady atmosphere of unbridled magnificence remains quite unchurchlike.