Spain and Morocco have taken a significant step toward building a submarine rail tunnel beneath the Strait of Gibraltar, reviving a decades-long ambition to create a fixed link between Europe and Africa.
A memorandum of understanding was signed between Spain’s National Geographic Institute and Morocco’s National Center for Scientific and Technical Research to carry out joint studies on the strait’s seismic activity and geodynamic conditions. The agreement was formalized on December 4, 2025, during a meeting in La Moncloa between Spanish Transport Minister Óscar Puente and Moroccan Minister Karim Zidane.
The tunnel project has been under consideration for nearly 50 years, since the two countries first agreed to explore a permanent connection across the strait. According to Spanish media reports, Madrid approved a further €1.73 million in mid-March 2026 to finance new technical studies. The work is being coordinated through SECEGSA, the state-owned Spanish company established in the 1980s to study a fixed crossing between Spain and Morocco.
Current plans envision infrastructure stretching roughly 65 kilometres, with around 40 kilometres on Spanish territory. The northern entrance would be located near Vejer de la Frontera. The distance between the terminal stations would be 42 kilometres, including 38.5 kilometres of tunnel, of which 27.7 kilometres would run underwater.
The tunnel’s deepest point would reach 475 meters below sea level, with a minimum rock cover of 175 meters and a maximum gradient of 3%. The design calls for two separate single-track railway tubes, each with an interior diameter of 7.9 meters, linked by a 6-meter-wide central service gallery for emergency access and maintenance.
Cross-passages, also 6 meters in diameter, would connect the two tubes every 340 meters. A secure parking zone would be installed at the tunnel’s lowest point, featuring stop areas, safety zones, intervention spaces, and a smoke extraction gallery.
SECEGSA has commissioned a feasibility study from Herrenknecht Ibérica, the Spanish subsidiary of the German tunnelling specialist, to assess whether excavation through the Umbral de Camarinal, an underwater ridge separating the Atlantic Ocean from the Mediterranean Sea, is technically possible.
The study concluded that the project is feasible within current engineering capabilities, although it warned that execution would involve major logistical and financial challenges. The Camarinal subsurface consists of complex Flysch formations, including sandstone and clay layers of turbiditic origin, overlain by more recent Pliocene and Quaternary deposits. These conditions create highly variable geological behaviour over short distances, making this one of the most technically demanding parts of the route.
The Spanish side of the project alone is estimated to cost more than €8.5 billion. If completed, the tunnel would cut travel time between Spain and Morocco to around 30 minutes. Current projections place completion between 2035 and 2040.
Under the memorandum, the two countries will carry out three years of studies focused on seismic risks, earthquakes, tsunamis, and the broader geodynamic behaviour of the strait. Spain’s National Geographic Institute has highlighted the area’s tectonic sensitivity, noting that the Iberian Peninsula lies along the boundary zone of major tectonic plates, including the Azores-Gibraltar-Tunis fracture system, which was linked to the catastrophic 1755 earthquake.
If the results are favourable, authorities could approve excavation of a reconnaissance gallery, with an initial tender potentially launched in 2027. That phase alone is expected to take between six and nine years.
A marine research campaign is also scheduled before the end of the first half of 2026. Commissioned by Spain’s Superior Council of Scientific Research with a budget of €553,187.38, the 15-day mission will include high-resolution seabed mapping, sub-bottom profiling, sediment and rock sampling, and laboratory analysis.
The campaign will be carried out by three CSIC institutes: the Institute of Marine Sciences, the Geological and Mining Institute of Spain, and the Spanish Institute of Oceanography. Spain’s Navy Hydrographic Institute and the United States Geological Survey will also take part as members of an international working group.
The Strait of Gibraltar presents additional operational and environmental challenges. More than 100,000 vessels pass through it every year, while the research zone is protected under a special conservation framework that includes measures for orca protection. More than 1,900 marine species have been recorded in the area, making environmental oversight a central part of the planning process.
All data gathered during the research phase will be used to build a three-dimensional geological model of the Umbral de Camarinal, regarded as a crucial tool for determining whether the tunnel can move from study to construction.
