The interior contains some outstanding artwork including an altarpiece by Sebastián Herrera and paintings by Claudio Coello, Herrera and Ricci. The decor is baroque, there are numerous side chapels, barrel vaulting and a huge dome. The façade features large built-in columns, a portico and a vaulted niche containing sculptures by Juan Pascual de Mena. It's also known as the Colegiata de San Isidro, as it was part of a college founded by the Jesuits in the 16th century. The remains of Madrid's patron saint, San Isidro, lie here.
Religious - Christianity