If you have visited the Descalzas, you might find its sister institution something of letdown. An Augustinian convent, founded in 1611 by Marguerite of Austria, wife of Felipe III, its main attraction is the harmonious design by royal architect Ventura Rodriguez, who rebuilt it after a fire in 1767. Between the privacy needs of the cloistered nuns and the painfully slow restoration that has been going on for decades, you see little but religious paintings on the 1-hour guided tour in Spanish. The highlight is the reliquary room, packed floor to ceiling with purported True Cross splinters, personal objects of saints, and innumerable chalices and monstrances. Perhaps the most intriguing relic is a vial of the blood of Saint Pantaleon. According to legend, it liquefies on July 26 each year, the eve of his feast day. If it does not, guides glumly warn, disaster is in the offing.