Lonely Planet review
Towering above the northern end of bustling Calle de Toledo, and visible through the arches from Plaza Mayor, this imposing church long served as the city’s de facto cathedral until Catedral de Nuestra Señora de la Almudena was completed in 1992.
Still known to locals as the Catedral de San Isidro, the austere baroque basilica was founded in the 17th century as the headquarters for the Jesuits and is today home to the remains of the city’s main patron saint, San Isidro (in the third chapel on your left after you walk in). His body, apparently remarkably well preserved, is only removed from here on rare occasions, such as in 1896 and 1947 when he was paraded about town in the hope he would bring rain (he did, at least in 1947). Official opening hours aren’t always to be relied upon.
Next door, the Instituto de San Isidro once went by the name of Colegio Imperial and, from the 16th century on, was where many of the country’s leading figures were schooled by the Jesuits. You can wander in and look at the elegant courtyard.