Water tank in the Parc de la Ciutadella

Barcelona was the principality of Catalonia's last bastion of resistance to Philip V's Bourbon troops during the War of the Spanish Succession (1701-1714). The monarch gave the order to build a barracks inside the military citadel so that his men could keep watch over the city. When the site of the citadel was returned to Barcelona in 1868, the city council embarked on a project for a city park designed by the architect and master builder Josep Fontseré i Mestre. The project required a generous water supply for the gardens and the monumental waterfall.

In 1876, Fontseré designed a monumental building to be constructed near the park. It would house a vast water tank measuring 65 metres on each side and hold 10,000 m³ of water. Steam engines would pump the groundwater into the open tank that was raised 14 metres above the floor and underpinned by a forest of brick pillars inspired by the Roman model of the Piscina Mirabilis in Bacoli, near Naples. Antoni Gaudí, who was a young architecture student at the time, performed the calculations about the weight of water the pillars would have to withstand.

Building work was completed in 1880 and, since then, the vast interior space between the pillars has had a number of uses. During the 1888 Universal Exhibition it housed the hall of mining and building. It was later used as a municipal nursing home, a warehouse for the fire brigade, a car park for the municipal police's fleet of vehicles and the archive for the law courts.

Pompeu Fabra University purchased the property in 1992 and the interior was respectfully restored in successive phases. It is now used as the general library. The tank on the roof, which has been reduced in size, was preserved and is still used to irrigate the gardens in the park.