The discovery of a hidden tunnel in Ceuta, ingeniously concealed within an old marble shop near the Moroccan border, was made by the Civil Guard on February 19. The narrow corridors, lined with wooden panels, were damp and constantly dripping with water. This made it impossible to inspect the tunnel immediately, as there was a risk of crossing the territorial boundary. As such, several days were necessary to pump out the water before the full investigation could be carried out.

On March 3, the Subsoil Recognition Unit of the Civil Guard conducted a thorough inspection. The video footage, seen by EL PAÍS, shows the tunnel's wooden walls, large hinges attached to the ceiling, and remnants of silicone. The infrastructure is equipped with its own lighting and water drainage system, using yellow pipes running along the floor. Witnesses describe the environment as extremely humid, with empty water bottles and a flooded area that marked the path. Remarkably, a suitcase was found during one of the inspections.

This tunnel was the culmination of Operation Hades, orchestrated by the Civil Guard's Internal Affairs Service. The operation, named after the god of the underworld, inferred a place of darkness. Investigators utilized intelligence from the Regional Center for Narcotics Analysis and Intelligence (CRAIN), which suggested the tunnel's existence, ultimately confirmed by their efforts.

The passage extends 12 meters deep and stretches 50 meters long, as reported by the Civil Guard on February 20. It features multiple galleries within Spanish territory, generally measuring 40 centimeters wide by 60 centimeters high, although dimensions vary across sections. Remarkably, certain areas allow individuals to stand upright, according to sources familiar with the police operation.