The Underwater Megatunnel That Could One Day Link Spain and Morocco by Rail

40 Years in the Making — and Engineers Say It Can Be Done

A plan to connect Spain and Morocco by rail through an underwater tunnel beneath the Strait of Gibraltar has been declared technically feasible by Spanish engineers — rekindling one of the most ambitious infrastructure proposals in European history.

The project has been on the drawing board since the early 1980s, but advances in modern engineering have brought it back into serious consideration. The organisation behind the proposal, SECEGSA (the Spanish Society for Studies of Fixed Communication of the Strait of Gibraltar), has confirmed that the tunnel can be built — and that construction could begin as early as 2027.

The Route and Scale

The tunnel would connect Punta Paloma, near Tarifa in southern Spain, with Malabata, near Tangier in Morocco — the two points where the Strait of Gibraltar is at its narrowest.

The key figures:

• Total length: approximately 42 kilometres
• Underwater section: 27.7 kilometres
• Maximum depth: 475 metres below sea level
• Estimated cost: between €7.5 billion and €10 billion

Rather than a single bore, the project calls for three separate tunnels: two dedicated to rail traffic and one reserved for emergency services — a configuration similar to the Channel Tunnel between the UK and France.

The Big Engineering Challenge: The Camarinal Threshold

The most significant technical obstacle is a natural underwater ridge known as the Camarinal Threshold — the point where the Mediterranean Sea meets the Atlantic Ocean. This geological feature lies directly in the path of the proposed tunnel and has been described as "a huge economic and logistical challenge" requiring specialised drilling techniques.

It is precisely this challenge that stalled earlier studies for decades. Engineers are now confident that modern tunnelling technology — developed and refined since the construction of projects like the Channel Tunnel — makes it possible to overcome.

Why It Matters

A fixed rail link between Spain and Morocco would be the first direct land connection between Europe and Africa. The implications go well beyond travel convenience:

• Trade: Goods currently shipped across the Strait could move by rail — faster, cheaper, and with a lower carbon footprint
• Passenger travel: A train journey between Madrid and Marrakech would become a realistic alternative to flying
• Strategic significance: The link would deepen economic integration between the EU and North Africa at a time when migration, energy supply and trade relations are all high on the political agenda

For southern Spain — particularly Andalusia and the area around the Campo de Gibraltar — a tunnel of this scale would represent a transformative economic opportunity, positioning the region as a gateway between two continents.

What Happens Next

The green light from SECEGSA engineers is a significant milestone, but it is important to be clear about where the project stands. Technical feasibility is not the same as a decision to build. The tunnel still requires political agreement between Spain and Morocco, detailed project planning, environmental assessments, funding arrangements, and procurement — a process that typically takes many years even after a project is declared viable.

With a potential construction start date of 2027 being cited, progress is expected — but a tunnel of this scale and complexity would take many years to complete once work begins. For now, the confirmation that it can be done is the story. Whether and when it will be done remains to be seen.

This article is based on reporting from Spanish News Today, published April 23, 2026.