Check Out The Largest Civil Engineering Project In Europe.

Crossrail Project

Set to open in 2018, the Crossrail expansion of London's rail network is the largest civil engineering project in Europe.

Once complete, 56 kilometers (35 miles) of new tunnels, stations and interchanges will connect the outer suburbs to the city center and Heathrow airport, nearly 40 meters (131 feet) below the city.

It is a huge feat of engineering with a budget of more than $20 billion. 

For those involved, the biggest challenge has come from working in a densely packed city such as

London, steeped in 1,000 years of industrial history.

"It's not just buildings or the underground, but utilities corridors. It has been the biggest challenge of my career," project manager Linda Miller told CNN.

At Farringdon station in central London, those working on the project refer to it as "the heart of the Crossrail." 

tunnel boring machine

Of the eight tunnel boring machines that set off from different parts of the city, four of them ended up in Farringdon: "Sometimes in this job it feels like you have landed on the moon, it's so unrecognizable" explains Miller, "(but) it's going to move from looking like the moon to a transportation system".