Pantheon of the Kings Monument · San Lorenzo de El Escorial, Cuenca del Guadarrama, Madrid Circular crypt beneath the high altar built between 1617 and 1654 to a design by Juan Bautista Crescenzi and executed by Juan Gómez de Mora; it combines black marble, reddish jasper and gilt bronzes around twenty-six sarcophagi. Photo: Bocachete (Public domain) What to see and do in San Lorenzo de El Escorial