The Sacred Art Museum, accessed through the church of the Mosteiro de San Paio de Antealtares, contains the Ara (Altar) de Antealtares, the original altar (a recycled Roman funerary plaque) raised over Santiago's relics. The church itself is of relatively simple design, except for its main altar, a frenzy of gilded baroque. You can stop by at 8pm (7.30pm Saturday and Sunday) to hear the nuns singing vespers.
Museo de Arte Sacro
Santiago de Compostela