The governments of Spain and Morocco have taken a significant step towards the realization of an ambitious project to build an undersea tunnel under the Strait of Gibraltar. A key step took place with the signing of the Memorandum of Understanding between the Spanish National Geographic Institute and the Moroccan National Center for Scientific and Technical Research on December 4, 2025.
Although the fixed connection between Europe and Africa has been discussed for almost half a century, the project gained new momentum only in March, when the agreement was ratified by the Spanish Government and an additional 1.73 million euros was approved for technical studies, which means that the first preparatory works can begin. The first three-year framework for joint research into the seismicity and geodynamics of the straits has been formally set, which is a critical prerequisite for the safety of future infrastructure.
A significant technological undertaking
The planned tunnel would have a total length of 65 kilometers, of which 40 kilometers would be on Spanish territory with an entrance near Vejer de la Frontera. The tunnel section alone between the terminal stations would be 38.5 kilometers, including 27.7 kilometers directly under the seabed. At the deepest point, the tunnel would reach 475 meters below sea level, while the minimum layer of rock above the pipe would be 175 meters with a maximum slope of 3%.
The infrastructure solution envisages two independent pipes for one-way rail traffic, each with an internal diameter of 7.9 meters. Between them, there would be a central service gallery with a diameter of 6 meters, intended for maintenance and emergency interventions. The connection of the main pipes is provided by cross passages every 340 meters, while at the lowest point a safe parking zone equipped with smoke extraction and evacuation systems would be built.
Geological challenges
The feasibility study confirmed that the project is technically feasible within the limits of modern engineering. Despite the positive assessment, experts warn of exceptional logistical and economic challenges due to the complex geological composition that includes deposits of sandstone, clay and younger Pliocene sediments with highly variable behavior. The National Geographic Institute of Spain reminds that the strait is located at the contact of tectonic plates, in a zone historically known for strong seismic activity.
It is estimated that construction costs on the Spanish side alone will exceed 8.5 billion euros. If the research proves successful, the first tenders for excavating the scout gallery could be announced in 2027, while the completion of the entire tunnel and the establishment of a 30-minute train journey between the two continents is expected between 2035 and 2040. In Morocco, they are somewhat disappointed that the tunnel will not be finished until the 2030 World Cup, which they co-host with their neighbor Spain.