Former Asturian coal shaft at Sama de Langreo, now housing the Archivo Histórico de Hunosa and the Brigada Central de Salvamento Minero, with geothermal and biomass energy installations.
Pozu Fondón, situated beside the river Nalón at Sama de Langreo, was the first vertical shaft sunk by the Sociedad Metalúrgica Duro Felguera and the second vertical coal shaft profundised in Asturias. The area had been mined from 1840 through the mountain mine of La Nalona. Duro Felguera acquired the mine in 1868 and began sinking two vertical shafts in 1905, with full production achieved by December 1917.
The shaft was integrated into Hunosa in 1967 and ceased extraction in August 1995. It reached a depth of 667 metres across nine working levels. During the post-war period it housed a penal colony for political prisoners until the end of 1958.
In 1994 Hunosa launched a project to rehabilitate the shaft buildings as the home of its historical archive. The Archivo Histórico de Hunosa was established in the pithead buildings from 1995 onwards and opened to the public in 2022. The site also hosts the Brigada Central de Salvamento Minero, geothermal and biomass energy installations, and a surviving headframe from the first shaft.
One of the two original headframes was dismantled in 1994.
The area between Sama and La Felguera in the concejo of Langreo was first exploited for bituminous coal through the mountain mine of La Nalona, opened around 1840. In 1868 the company Duro y Cía, which would become the Sociedad Metalúrgica Duro Felguera in 1900, acquired the La Nalona mine from a group of private owners. In 1905, by this time operating as Duro Felguera, the company began the profundisation of two vertical shafts at the site, establishing the Pozu Fondón as the second vertical shaft in Asturias and the first owned by Duro Felguera. A 1910 tunnel was constructed to connect the shaft to the railway that transported coal to the Lavadero de Modesta; the entrance arch bears the company initials and the year of construction on its keystone. Full production was achieved in December 1917.
The winding engine house at the shaft dates from approximately 1910, with an extension added in 1935. The buildings, constructed throughout in the Duro Felguera house style of red exposed brick combined with natural stone for plinths and decorative window surrounds, form an architecturally coherent ensemble. The forge building dates from the 1920s. The offices and washhouse were built in the 1930s, and the workshop and powder magazine in the 1940s. The loading bays, designed by the architect Juan José Suárez Aller, were constructed in the mid-twentieth century and incorporate tympanum mosaics of mining iconography by the artist Luis Suco-Sánchez; two of the three mosaics survive, the third having been damaged in an explosion in the 1980s.
The auxiliary headframe, designated castillete número 2, was installed around 1916, replaced in 1947, and dismantled in April 1993, a year before extraction ceased. The winding machinery for both headframes was manufactured by Siemens of Germany. Shaft number 1, the main extraction headframe, is of riveted iron construction, 31 metres in height to the pulley axis, serving a shaft of 5 metres diameter and 583 metres depth across ten working levels, used for ventilation intake. Shaft number 2 was 28 metres to the pulley axis, with a diameter of 3.8 metres, 378 metres deep and seven working levels, used for extraction.
During the Spanish Civil War and its aftermath, the shaft was used as a penal colony under the Francoist system of redemption of sentences through labour. Political prisoners worked the mine for token wages that were far below those of other miners. The penal colony was closed at the end of 1958.
The Pozu Fondón was integrated into Hunosa in 1967 along with the other Duro Felguera mining assets. As part of the restructuring associated with the Plan de Empresa (1994–1997), the shaft ceased to operate as an extraction unit in August 1995, with production concentrated at the Pozo Candín. The shaft reached a total depth of 667 metres across nine working levels during its operational life and was served by a workforce of approximately 700 at its peak.
In 1994 Hunosa identified the closed shaft's buildings as a suitable location to centralise its historical documentation, and in 1995 the Proyecto para la Rehabilitación Integral del Pozu Fondón was launched. The rehabilitation was directed by the Asturian architect Miguel García-Pola Vallejo, whose team won the design competition. From 1995 the pithead buildings were progressively adapted to house the Archivo Histórico de Hunosa and the Centro de Documentación. The archive holds the collections of more than thirty historical mining companies, covering documentation generated before Hunosa's creation in 1967. The archive was opened to the public in February 2022, with guided visits available from March of that year. A major works programme completed in 2023 upgraded the buildings for energy efficiency and environmental standards.
The Brigada Central de Salvamento Minero, which had been based at the shaft since 1920, continues to operate from the site. Geothermal energy installations using the flooded shaft water to provide district heating for nearby buildings were commissioned in 2022, and a biomass energy plant using Asturian forestry residues was also established in the loading bays. A hydrogen production plant was under construction at the site as of early 2022. The surviving headframe of shaft number 1, with its pulley wheel placed ornamentally at the forge entrance, remains standing at the site. The bocamina of the original La Nalona mountain mine is also preserved and restored within the compound.