This octagon is surrounded by an ambulatory with complex vaulting. At the south wall stand a row of recessed arches with the tombs of the four younger sons of John I, together with their spouses. From left to right: Ferdinand the Holy Prince (a bachelor, he died a prisoner in Fez in 1443; his bodily remains were later recovered and moved here in 1473); John of Reguengos, the Constable of Portugal (d.1442), with his wife Isabella of Barcelos (d.1466); Henry the Navigator (under a baldachin, d.1460, a bachelor); and Peter of Coimbra (regent for Afonso V, 1438–1448, who was killed at the Battle of Alfarrobeira in 1449; his remains were moved here in 1456) with his wife Isabella of Urgell (d.1459).