This chapel, in the apse of 14th-century Basilica di San Francesco, safeguards one of Italian art's greatest works: Piero della Francesca's fresco cycle of the Legend of the True Cross. Painted between 1452 and 1466, it relates the story of the cross on which Christ was crucified. Only 25 people are allowed in every half-hour, making advance booking (by telephone or email) essential in high season. The ticket office is down the stairs by the basilica's entrance.

This medieval legend is as entertaining as it is inconceivable. The illustrations follows the story of the tree that Seth plants on the grave of his father, Adam, and from which the True Cross is made. Another scene shows the long-lost cross being rediscovered by Helena, mother of the emperor Constantine; behind her, the city of Jerusalem is represented by a medieval view of Arezzo. Other scenes show the victory of Heraclius over the Persian king Khosrau, who had been accused of stealing the cross; Constantine sleeping in a tent on the eve of his battle with Maxentius (note Piero's masterful depiction of the nocturnal light); and Constantine carrying the cross into battle.

Two of the best-loved scenes depicts the meeting of the Queen of Sheba and King Solomon. In the first half she is kneeling on a bridge over the Siloam River and meeting with the king; she and her attendants are depicted wearing rich Renaissance-style gowns. In the second half, King Solomon's palace seems to be modelled on the designs of notable architect Leon Battista Alberti.