The water company, Canal de Isabel II, had to keep up with Madrid's expanding population and water needs and constructed reservoirs (in the Mountains of Madrid), canals and aqueducts throught the 19th century. The first main deposit was amost in the centre of the city and opened in 1858. This is the second and the third was opened in 1905 (I have posted shots of its water tower). Since the 1950s, the water system has expanded exponentially. Deposits I, II and III have long been defunct. This is being transformed into a park and could open soon, Covid-19 permitting.