HS2 Ltd has started construction of an innovative green tunnel designed to blend the railway into the landscape.
The one-and-a-half-mile-long structure in Chipping Warden, Northamptonshire, is being built on the surface of the ground to speed up the process.
More than 5,000 concrete segments made in a factory in Derbyshire will be assembled on site, before being covered by earth, trees, shrubs and hedgerows to fit in with the surrounding countryside.
The overall project has faced fierce criticism about the impact it will have on the route of the line.
The green tunnel will be an m-shaped double arch with separate halves for northbound and southbound trains.
Both halves will be the height of two double-decker buses.
The tunnel is the first of its kind in the UK.
Construction is expected to last three years.
A total of five green tunnels will be part of Phase One of the high-speed railway between London and Birmingham.
HS2 Ltd’s project client Rohan Perin said: “The Chipping Warden green tunnel is a great example of what we’re doing to reduce disruption for people living close to the railway – and it’s fantastic to see the first arches in position.
“Our trains will be powered by zero carbon electricity but it’s also important to reduce the amount of carbon embedded in construction.
“The off-site manufacturing techniques being used will help cut the overall amount of carbon-intensive concrete and steel in the tunnel and make the whole process faster, more efficient and therefore less disruptive for the community.”