Librería Calatrava, the oldest bookshop in Madrid, contains an endless source of fascinating literature. It was founded by the protestant cleric Federico Fliedner, and was initially known as Librería Nacional y Extranjera (National and Foreign Library).

Specializing in the protestant religion since its beginnings in 1873, today it offers a wide range of books on all religions and various other topics. The staff is noted to have an extensive knowledge of local authors as well.