A television news crew has crossed the sealed walls of the Cuelgamuros crypts for the first time in nearly six decades to film a new feature documentary about Spain's largest Civil War mass grave. Journalist Belén Alonso and director Manuel Diéguez led the project for DocumentaRTVE, capturing footage inside the monument near Madrid for their film titled Cuelgamuros: entre lo difícil y lo imposible.
The documentary records the work of forensic scientists operating inside sealed vaults that have remained closed to visual media since 1959. Cuelgamuros holds the remains of more than 33,800 Civil War victims, including at least 12,000 unidentified individuals. Before this project, the only existing images of the interior were isolated black-and-white photos taken by the EFE news agency when the first transport trucks arrived in 1959.
Filming inside the underground crypts required a complex logistical operation due to extreme environmental conditions. The crew worked in total darkness with a relative humidity level of 90 percent inside narrow chambers that measure barely six meters wide.
The production team also had to follow a strict Level 2 biosafety protocol. Crew members wore protective suits to prevent contaminating bone remains that had scattered outside more than 11,000 wooden boxes stacked behind the walls.
Forensic work inside the Chapel of the Holy Sepulchre
Much of the film focuses on the Chapel of the Holy Sepulchre, which has been converted into a temporary high-precision laboratory. More than 18,000 bodies rest inside this single chapel. Since 2023, a multidisciplinary team of anthropologists and forensic experts has been working there to identify 214 victims requested by their families.
To capture the research without disrupting scientific work, the crew placed tiny cameras overhead on the ceilings. These fixed cameras recorded the harsh physical environment alongside emotional moments when scientists achieved positive identifications.
Historical archives and premiere at San Sebastián
Cuelgamuros, previously known as the Valley of the Fallen, was built during the dictatorship of Francisco Franco following the Spanish Civil War, which took place from 1936 to 1939. RTVE, Spain's state broadcaster, produces documentary content through its DocumentaRTVE unit to record major national historical events.
The film avoids a purely institutional format by blending field research with personal testimonies and historical archival footage from NO-DO, the state-run newsreel service used during the Franco regime. Spanish authorities granted access for this project after decades of denying requests from international news organizations and independent production companies.
The completed documentary will premiere at the 74th San Sebastián International Film Festival. Organizers have scheduled the initial screening for September 22, prior to the film's national broadcast on open television.
The San Sebastián International Film Festival is held annually in the Basque city of San Sebastián in northern Spain and ranks among the most prestigious cinema events in Europe.
