The San Gil barracks were designed by Francesco Sabatini and stood in the northern part of what is now the Plaza de España. The barracks were demolished at the beginning of the 20th century.

Construction of the San Gil barracks began in 1789. Originally conceived by architect Manuel Martín Rodríguez as a convent for Franciscan monks. The building was demolished for the first time and then rebuilt as a settlement for the army. The idea was to defend the northeast flank of the Royal Palace. The final building was the work of prominent Italian architect Francesco Sabatini

After over a century of military use, the demolition of the barracks was decreed in 1903. This finally began in 1906 and was not completed until 1908.

A recent refurbishment of the Plaza de España, which started in 2020, led to the discovery of some important archaeological remains. One example is a series of walls made up of semicircular arches that correspond to part of the San Gil Barracks, which after 118 years underground, have now been relocated to the surface.