|The Unesco note this on their site on historical mining heritage in Spain here
The mining basin is comprised of a huge hypogenic mass running NW to SE. Its southern edge is in contact with a more recent formation which is the base of the coal deposit. In this basin, coal sediments are broken down into three groups: base gaps, production face and ceiling conglomerates.
Coal mining commenced in 1621 when King Phillip Ill issued a Royal Order calling for exploitation of the coal basin. The Royal Artillery Petty Officers of Seville worked the mines from 1740 to 1803 and initiated the industrialisation process which was taken up by the Guadalquivir Company until 1815. The Company known as Minas de la Reunion formed in 1839, merged in 1867 with the Madrid, Zaragoza y Alicante railway company (Spanish acronym M.Z.A.) and operated until 1969 when it was taken over by the State.
The mining systems employed were "tajos en direccibn por hundimientos" (without the use of backfill) and the so-called "huecos y pilares" system implemented by the Navegacion del Guadalquivir mining company.
As for the technological and industrial aspect, the mining complex conserves the print of the major technical advances of the end of the 191h century in terms of machinery, energy supply and extraction systems. Special mention should be made of the remains at shaft No 5 which include the metallic extraction crane powered by the Bollinclx (1922) steam engine, the engine house, sieves and washing tanks, a Babcok Wilcox boiler, Kaselowsky drainage pump house, Schlamms tanks (coal sludge decantation reservoirs) and the electical power plant (1926). Shaft No 7 features the water tower (1928), the crane andengine house (1926-28), energy distribution tower (1929), electrical power plant and workshop buildings. The bulk of these installations are housed in historicist-style buildings most of which are of brick although there are some elements of the modernist movement arising from international rationalism; iron architecture can also be found.
This is one of the most valuable sets of mining homes in all of Andalusia, an example of the developmentalist models in vogue in the 191h and beginning of the 20" centuries. The residential area is comprised of the following developments: Confianza, built between 1896 and 1900 to replace the primitive barracks; Velarde and Constancia, built during the last decade of the lgth century to house drill and pick operators; and Progreso, Cerro, Balbo and Transwall dating back to 1935. The development is topped off with the neighbourhood known as Casas Nuevas, the most interesting from an artistic point of view built in the 1920's as residences for company executives and skilled workers, special mention being made of the Administrative House, a square chalet with a merlon-shaped tower rising above the garden and the modernist Chief engineer's House. Other noteworthy buildings include the church, built in 1927, the school and the theatre-cinema.