Designed by the architect Antonio Palacios, the building was build between 1904 and 1918. The architectonic style is eclectic, mixes of different architectonic tendencies and composition styles from Europe and North America, characteristic of the first years of 20th century. The building pretends to be enormous, without being it in fact; this monumental character comes from its ascending volumetric composition from the three plants corners until the central clock tower, authentic "urban light", that duplicates its height here.
The main facade to the Cibeles has a smooth concave form related to the ellipsoidal form of the Public square. 

In the building there is a Postal and Telegraphs Museum.

From the stamp sheet edition "150 Aniversario del primer sello español - 2000"