World's longest railway tunnel cost £11.2bn to build and is thousands of feet below ground

A decade ago this month, work concluded on one of the globe's most remarkable engineering achievements. The Gotthard Base Tunnel - a railway tunnel beneath the Lepontine Alps in Switzerland - stands as the longest and deepest transport tunnel on Earth.

It became operational in June 2016 and has delivered a high-speed rail connection linking northern and southern Europe. More precisely, the service operates between Rotterdam in the Netherlands and Genoa in Italy. It's termed a Base Tunnel because it passes through the mountain's base, rather than attempting to wind over the peaks.

This ensures that the route through this train is largely straight and level.

The high-speed services that pass through it can reach 250km/h, dramatically reducing journey times.

Building this remarkable tunnel required an enormous 17 years of non-stop work and roughly CHF 12.2 billion (£11.2billion) to complete.

Construction teams and engineers removed over 28 million tonnes of rock, employing massive boring machines to excavate it, alongside precision blasting to forge the tunnel's path.

Prior to its creation, trains were forced to navigate the twisting mountain pathways, which meant travel velocity and freight capacity were substantially limited.

Today, trains can zip through solid rock and cover the distance from Erstfeld in the North to Bodio in the South in merely 20 minutes.

This extraordinary tunnel stretches for 57km, and at its deepest section, it lies thousands of feet underground. At its lowest point, trains pass through at a depth of 7,546 feet below the surface.

Since it was built, the tunnel has transported vast numbers of passengers, with figures revealing that the volume of travellers passing through the Gotthard by rail has nearly doubled over the course of a decade.

In 2025, the average was 16,400 a day, compared with 9,000 in 2015, according to the Swiss Federal Railways.