A massive underground railway stretching nearly ten miles beneath one of Africa's busiest and most populated regions has transformed how millions of people move every year. Costing around £2.6 billion to build, this tunnel forms the backbone of the Gautrain project in South Africa and stands as the longest underground rail tunnel on the entire continent.

Running beneath Gauteng province, the 9.6-mile tunnel links three major underground stations: Johannesburg Park, Rosebank and Sandton. Every day, thousands of commuters rely on the system to travel quickly and reliably between work, home and key services.

The tunnel is part of the wider Gautrain network, a 50-mile high-speed rail system designed to ease pressure on overcrowded roads.

The express commuter rail system links Johannesburg, Pretoria, Kempton Park and OR Tambo International Airport. It takes 15 minutes to travel from Sandton to O. R. Tambo International Airport on the Gautrain and 35 minutes from Pretoria station to Park Station in Johannesburg.

Trains operating through the tunnel can reach speeds of over 99 miles per hour, dramatically cutting journey times and helping reduce dependence on private vehicles.

Constructing a tunnel of this size, however, was no small task. Engineers had to cut through layers of rock and soil beneath a densely built environment, using a combination of tunnel boring machines and traditional drilling and blasting methods.

Absolute precision was essential and even small alignment errors could have caused serious structural problems.

The building and tunnelling stages of the project represented a significant engineering achievement and were carried out in carefully planned phases between 2010 and 2012.

In early 2025, Gautrain services between Park Station and Rosebank were briefly halted after water and soil seepage was discovered inside the tunnel.

Investigations revealed the damage had been caused by illegal borehole drilling on nearby private property, which compromised part of the tunnel structure.

Emergency bus services were introduced while repairs were carried out. Once repairs were completed, normal train operations resumed, and authorities indicated at the time that legal action may be taken against the property owner responsible for the drilling.