Built to protect the civilian population from military attacks and aerial bombings during the Spanish Civil War. Construction began in 1937 and continued after the war due to fears of an attack during World War II, despite Spain's neutrality.
The shelter had two entrances, one at Pla de l’Església and another at Sa Plaça, where the “Círculo Monárquico” was located. Its construction involved hand chiseling and the use of dynamite to break through the rock. The leftover material was removed with baskets through a human chain.