Under proposed changes to the route between Amersham and Wendover in Buckinghamshire Mr Hammond said there were opportunities for a "green bridge" over the cutting and a longer "green tunnel".

BBC: Changes to planned high-speed rail route unveiled

Then, inspired by NYC's High Line, Fletcher Priest won the Green Infrastructure Ideas Competition with his proposal for an underground mushroom tunnel beneath the streets of London.

ENGADGET: Inhabitat's Week in Green: Bicymple, computer-age fossils and an underground mushroom tunnel

Declared the European Green Capital in 2010, Stockholm is investing in new construction like the City Line tunnel, which will put commuter rail lines underground and double the number of trains able to move through the city.

BBC: Living in: Stockholm

It's on a big green sign right before you enter the Lincoln Tunnel.

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Beaminster business owner Claire Feasey, of Green Drawers, said she was closing her shop at the end of the year partly because of the tunnel closure.

BBC: Rosemary Snell - SWNS.com