Below the Almudena Cathedral lies this beautiful Romanesque Revival church with a Latin-cross plan. It features over 400 columns, each crowned by a different capital adorned with biblical figures, nature scenes and even the symbol of Madrid, the bear and the strawberry tree.  

It has the same dimensions as the cathedral and is considered to be the largest crypt in the country. The entrance, which is located in front of the Arab Wall, is made up of three semi-circular arches. The resting place of some of Spain’s most noble families, and to King Alfonso XII's first wife María de las Mercedes de Orléans. It has five naves and 20 chapels along the sides. Artists such as Benlliure created the relief work, and Maumejean provided the magnificent stained-glass windows that illuminate the chapels. The decoration of the oldest chapels mixes mosaics in the Byzantine tradition with reliefs and images of classical proportions, as well as Gothic-style stained-glass windows. The votive lamps hanging from the ceiling are inspired by the treasure of Guarrazar, found in Toledo in the mid-19th century. Particularly noteworthy is the painting of Our Lady of the Lily, possibly the oldest image of the Virgin in the city.