London could be the venue for a "garden bridge" in the mode of New York's High Line, if designer Thomas Heatherwick (he of 2012 Olympic cauldron fame) has his way. If £60 million (US$94 million) in private funding can be secured, it's thought the bridge could open as early as 2016.
The original idea for a green bridge, several years old according to the Evening Standard, appears to have come from actor and campaigner Joanna Lumley. "It's quite strange to talk of something that doesn't exist yet [we can definitely relate – Ed], but the Garden Bridge is already vivid in the plans and the imagination," she said. "It will be the slowest way to cross the river, as people will dawdle and lean on parapets and stare at the great cityscapes all around; but it will also be a safe and swift way for the weary commuter to make his way back over the Thames. There will be grasses, trees, wild flowers, and plants, unique to London's natural riverside habitat."
And that's almost as much as we know about the bridge itself at this point. The Standard reports that the plan is for the bridge to cross the Thames near to Covent Garden (presumably next or near to Waterloo Bridge).
Heatherwick Studio is now working with Arup to develop the proposal ahead of a formal planning application in early 2014. However, the longterm prognosis very much depends on finding that £60 million.