Build a hill and they will come. This, at least, is what Westminster council is betting on, having lavished £2m on a temporary mound. Rearing up at the western end of Oxford Street as a faceted green shell, looking like a landscape from a low-fi video game, the 25-metre high Marble Arch Mound is one of the more unlikely strategies for stimulating our Covid-stricken high streets. “You have to give people a reason to come to an area,” says Melvyn Caplan, the council’s deputy leader. “They’re not just coming to Oxford Street for the shops any more. People are interested in experiences and destinations.” The pandemic has seen around 17% of stores on London’s most famous shopping street close completely. The mound, it is hoped, is the kind of novelty experience that will lure people back to the West End, providing an opportunity for highly shareable Instagram moments, beyond selfies with armfuls of Selfridges bags. From Monday, having booked in advance and paid the £4.50–£8 ticket fee, visitors will be able to climb up a staircase that winds its way to the top of the scaffolding hill (or take the lift), enjoy elevated views of Hyde Park, post some pics, then descend a more fire escape-like staircase into an exhibition space and cafe. It is an extreme example of the kind of funfair brand of “experiential” urban set-dressing made popular by social media. But it was supposed to be even more radical. “We originally wanted the hill to totally cover the arch,” says Winy Maas, founding partner of MVRDV, the Dutch architecture firm behind the pop-up hillock. “That was an interesting discussion, let me put it that way.” Conservation experts advised that shrouding the almost 200-year-old stone structure in total darkness for six months could risk weakening the mortar joints, leading to potential collapse. The solution was to slice off the corner of the hill instead, leaving room for the arch and making the mound look like a computer model caught midway through rendering, revealing the wireframe scaffolding structure beneath. If the hill’s low-resolution polygonal form gives it a retro vibe, there’s a reason. For Maas, the project represents the fruition of an idea concocted almost 20 years ago, when his firm proposed to bury London’s Serpentine Gallery beneath an artificial hill for its summer pavilion in 2004. It was designed to be supported by a steel frame, rather than scaffolding, so the budget spiralled out of control and the scheme was scrapped, living on in the gallery’s history as the phantom pavilion that got away. Seeing the Marble Arch Mound a few days before it opens to the public, it’s hard not to wonder if it might have been better for it to remain that way. Architects’ slick computer images have a tendency to paint an optimistic picture, and this is no exception. While the CGI plans depicted a lush landscape of thick vegetation, dotted with mature trees, the reality is thin sedum matting clinging desperately to the sheer walls of the structure, punctuated by occasional spindly trees. The recent heatwave hasn’t helped, but none of the greenery looks happy. “It’s not enough,” admits Maas. “We are all fully aware that it needs more substance. The initial calculation was for a stair, and then there are all the extras. But I think it still opens people’s eyes and prompts an intense discussion. It’s OK for it to be vulnerable.” The trees will be returned to a nursery when the hill is dismantled, and the other greenery “recycled”, but it remains to be seen what state they’re in after six months perched on scaffolding. It’s a question that also hangs over this summer’s temporary forest at nearby Somerset House, or the collection of 100 oak saplings outside Tate Modern – all of which make you think trees are probably better off left in the ground. MVRDV were approached by the council after one of its officers saw their temporary staircase project in Rotterdam in 2016, which was a brilliant moment of urban whimsy. Coming out of the station, visitors were greeted with a colossal scaffolding staircase, 180 steps leading to the 30-metre-high rooftop of a postwar office block, from where sweeping views of the city could be taken in. Climbing its steep incline had the momentous processional feeling of scaling a Mayan temple, and it prompted a citywide discussion about how Rotterdam’s 18 sq km of flat rooftops could be used, spawning numerous initiatives and adding momentum to an annual rooftop festival. Could the mound have a similar effect in London? Will we see the city’s recent low traffic neighbourhood roadblocks swell into miniature mountains? Probably not. But beyond offering a momentary diversion from shopping, the project is intended to raise a bigger discussion about what form the future of this unlovely corner might take. “We’re not planning a permanent mound,” says Caplan, “but we are looking at ways to improve the gyratory and bring more greenery to Oxford Street.” The project is part of an £150m programme of public realm improvements, which have already seen pavement widening and temporary “parklets” introduced along the street in an attempt to cheer up the relentless gutter of buses, taxis and cycle rickshaws. A competition to design a partial pedestrianisation of Oxford Circus is launching later this year, too. But Marble Arch is a trickier proposition. It has long been marooned at the swirling confluence of several busy roads, victim of the plans of postwar highway engineers. The arch itself was originally designed by John Nash in 1827 as a monumental entrance to Buckingham Palace, but it was moved to this corner of Hyde Park in 1850 to form a grand gateway for the Great Exhibition. It remained as an entrance to the park for more than 50 years, but a new road layout in 1908 left it cut off, exacerbated by further road widening in the 1960s. Plans were drawn up in the 2000s to connect the arch back to the park, with a scheme designed by John McAslan as part of mayor Ken Livingstone’s 100 Public Spaces programme. Like many of Ken’s promised parks and piazzas, it was more blue-sky thinking than hard-nosed proposal, and the £40m to fund the project never materialised. Instead, 17 years later, we have a temporary hill-shaped attraction, confined to the roundabout, which does little to change the experience of crossing the congested arteries of traffic. Maas, however, believes the mound could inspire bigger thinking. “Imagine if you lifted up Hyde Park at each of its corners,” he enthuses, with his typical boyish wonder. “Speaker’s Corner could be transformed into a kind of tribune, with a perfect view across an endless landscape.” Over the years, his enthusiasm has bewitched many clients into buying into MVRDV’s particular brand of landscape alchemy. The son of a gardener and a florist, with an initial training as a landscape architect, Maas has always approached buildings as landscapes first and foremost. MVRDV’s first project in 1997 was a headquarters for Dutch public broadcaster VPRO, which appeared to lift the ground and fold it back and forth to form an office building, topped with a thick grass roof. More recently, they have built a museum storage building in Rotterdam shaped like a salad bowl crowned with a surreal floating forest, and are now completing the Valley in Amsterdam, a big mixed-use development smothered in plants. They join a plethora of green-fingered real estate ventures, from Stefano Boeri’s “vertical forest” apartment blocks in Milan and China, to Thomas Heatherwick’s 1,000 Trees project in Shanghai, which sees trees imprisoned in concrete pots on stilts in an attempt to disguise the massive mall beneath. Isn’t it all just greenwashing, though, using a superficial eco-garnish to distract from the tonnes of carbon-hungry concrete and steel below? “Our initial research shows that greening buildings can have a 1C cooling effect,” Maas says, “so it could be a significant step towards combating the urban heat island. Even the developers who just use it to camouflage their buildings a bit, at least it’s a start. You can kill the baby before it’s born, but I want to defend it.” The Marble Arch Mound, London, opens 26 July to January, book tickets online.