Let's make a stop at this Collegiate Church - one degree below a Cathedral - for two significant reasons, as it is the most important monumental church of Madrid's Baroque period and houses the remains of the city's patron saints, San Isidro and Santa María de la Cabeza, in the main altar since 1767. This building was erected as the Imperial College of the Society of Jesus between 1622 and 1664 by the Jesuit architects Pedro Sánchez and Francisco Bautista, and after the expulsion of the order, it was transformed into the Collegiate Church of San Isidro, where the original Jesuit College was located and where personalities of the Golden Age such as Lope de Vega, Quevedo, or Calderón de la Barca studied. Additionally, it served as the Cathedral of Madrid from 1885 until the inauguration of the Almudena Cathedral in 1993.