The pantheon of the Dukes of Osuna was built in Plateresque style in 1545. The first crypt is approached by a delightful patio with marble arcades. The chapel, stands just below the Colegiata's main altar and is crowned by a blue and gold polychrome coffered ceiling (coro) now blackened by candle smoke. In the second crypt are the tombs of the most important dukes of Osuna and the founders of the Colegiata.