Colegiata de San Cosme y Damián

This evocative 15th-century Gothic church is home to Spain's oldest still-functioning church organ, and has a gloriously ostentatious altar, fronted by several Roman stone tombs, plus that of Fernán González, the 10th-century founder of Castilla. Don't miss the graceful cloisters and the sacristía (sacristy) with its vibrant 15th-century paintings by Van Eyck and tryptic Adoración de los Magos. Entry is by guided visit only – check at the tourist office for tour times.