Cities want more green spaces, but there’s no place left to build. What’s a municipality to do? If they’re London, they look to the River Thames. It’s one part of the city center that’s relatively untouched by development.

A few years ago, London came up with a solar-powered railway station on one of its oldest bridges. Now, it has plans for an even greener crossing: the Garden Bridge, pictured here.

Image: Arup

Like New York’s High Line but built from scratch, the Garden Bridge would stretch 1,200 feet across the Thames, and contain a mass of flowers, grasses, shrubs, trees, walkways, and benches. The project’s backers hope it will be a slow and peaceful oasis amid the chaos of Europe’s busiest city.

The concept comes from Thomas Heatherwick, the British designer who recently remodeled London’s famous double-decked buses. His bridge design has large fluted piers that bulge at two points, creating more space for greenery. The span would go from the Temple area on the north side to the South Bank. Arup, the engineering firm, is assisting with the technical design.

Boris Johnson, London’s flamboyant mayor, is behind the project, but is not prepared to put up any public money. The Garden Bridge Trust needs to raise about $100 million to see it go ahead. Heatherwick hopes to finish his plans next year and complete the bridge in 2016.