Subterranean Park and Mushroom Farm ‘Popping Down’ in London

Popping up might be all the rage at the moment, but Londoners are on their way to developing an appetite for Popping Down. Soon, their city will see a new underground public space, with a disused tunnel being transformed into a subterranean walkway, lined with urban mushroom patches.

Last year, the Landscape Institute, in conjunction with the Green Museum and the Mayor of London, ran the High Line for London Competition, an open call for ideas for green infrastructure. According to the contest guidelines, submissions did not need to "be constrained by any restrictions such as current planning law, land ownership, budgets or health and safety issues".

Of the 170 entrants, Fletcher Priest Architects came out on top. The tunnel central to their plan is known as the 'mail rail' and runs under Oxford Street. Posties once used it to enable speedy delivery of letters and parcels between Paddington and Whitechapel, avoiding London's over-crowded streets.

Pedestrians will enter and exit 'Pop Down' at street level. Above ground, a sequence of glass-fibre mushroom sculptures will delineate the passageway, simultaneously letting in controlled amounts of light, to be supplemented by interior fibre optics. What's more, there'll be a chance to sample some subterranean goodness, with pop-up 'fungi' cafes at the tunnel's entrances sourcing their produce from below.

The competition was inspired by New York City's 'High Line', a public park constructed on an abandoned freight train railway elevated above Manhattan's West Side. In winning, Fletcher Priest beat a 20-strong shortlist of impressively creative rivals. The runner-up was Y/N Studio, with its 'Lido Line' plan, which would have seen the construction of a clean basin in the Regent's Canal, enabling water babies to swim to and from work.