Carlos V commissioned the cathedral in 1521 because he considered the Royal Chapel "too small for so much glory" and wanted to house his illustrious late grandparents someplace more worthy. Carlos undoubtedly had great intentions, as the cathedral was created by some of the finest architects of its time: Enrique Egas, Diego de Siloé, Alonso Cano, and sculptor Juan de Mena. Alas, his ambitions came to little, for the cathedral is a grand and gloomy monument, not completed until 1714 and never used as the crypt for his grandparents (or parents). Enter through a small door at the back, off the Gran Vía. Old hymnals are displayed throughout, and there's a museum, which includes a 14th-century gold-and-silver monstrance (used for communion) given to the city by Queen Isabella. Audio guides are available for an extra €3.