Restored with relish, the unhappy 1990s gallery is now proudly of its place. With eye-popping interiors inspired by a 1978 Habitat catalogue, this is a shining temple to Milton Keynes’ mythology

Home to Buckinghamshire’s leading collection of roundabouts and an army of mirror-clad retail sheds that seems to march for an eternity, Milton Keynes has long been the butt of sneering metropolitan jokes. A garden city dominated by roads, where pedestrians are shuffled through underpasses, it is the British experiment in modernity which proved that, unlike our mainland European cousins, we were never cut out to be modern.

But a new £12m reboot of the city’s contemporary art gallery aims to celebrate the weird and wonderful quirks of the 1960s new town in all its undervalued suburban glory. The new-look MK Gallery is a shining temple to the curious mythology of the place, an unapologetic hymn to the land of big boxes and concrete cows.

“We wanted the building to be utterly Milton Keynesian,” says the gallery’s director, Anthony Spira. It is not something that many architects have aspired to, but Tom Emerson of practice 6a took on the brief with relish.

“Milton Keynes has a fascinating origin story,” says Emerson, “combining the English landscape tradition with the invention of leisure, American modernity and many other ideals. We have tried to tell its history over the decades in the form of our architecture.”

Facebook Twitter Pinterest A gloriously 70s vision that would have made the young Terence Conran proud … MK Gallery’s sky room. Photograph: 6a

He is standing in the gallery’s new cafe, where the bright red-painted steel structure, yellow furniture and dangling globe light fittings are a reference to the jazzy interior of the city’s former architecture department – an unlikely early work of Norman Foster nicknamed the Custard Factory. Outside, marking the entrance to the gallery, stands a replica of one of Milton Keynes’ distinctive flat-roofed roadside canopies (or portes-cochères), which are dotted along the city’s broad avenues like little homages to Mies van der Rohe. The bulk of 6a’s extension, meanwhile, takes the form of a big box clad in profiled, mirror-polished steel, its facade inscribed with the rectilinear grid so characteristic of the city’s early buildings, from the train station to the gigantic shopping mall, and punctuated by a huge circular window. It is proudly of its place, standing as a sharp, purist foil to some of its clumsy neighbours.

It is particularly refreshing because, for the past 30 years, the city’s architects and planners seem to have studiously avoided being Milton Keynesian. While the 60s masterplan took its inspiration from the American urban grid, seeing long avenues lined with low-rise glass blocks, the 90s saw a conscious backlash against the right angle. There was a proliferation of swoopy rooftops and curving facades, with buildings doing everything they could to break from the relentless grid.

The original MK Gallery is itself an unhappy product of this era, built in the late 90s as an afterthought to a theatre complex, crammed into a small building that cowers beneath a ridiculously oversized blue steel canopy. The architects have stripped back the interiors of the existing galleries and cut new openings to make a long linear axis through the rooms, in a nod to the city’s axial layout with its uninterrupted views, although some of the awkwardness of the original building remains.

Artists Nils Norman and Milton Keynes-born Gareth Jones have collaborated with 6a to devise an eye-popping colour palette for the interior, based on a colour chart they found in a 1978 Habitat catalogue. It sees the stairwells painted candy pink, dairy cream and canary yellow, along with toilets decked out in a psychedelic spectrum, from orange and pillar box red to burgundy, peppermint green and chocolate. It is a bold leap for 6a, who are usually subtle purveyors of various shades of grey, but a very welcome one for our mostly colour-starved times – although it may be too much for those who experienced the era of avocado bathrooms and brown-and-orange conversation pits the first time around.

Facebook Twitter Pinterest Makes you long for an emergency drill … MK Gallery’s stairwell. Photograph: 6a

When you reach the “sky room” on the first floor, you find a sumptuous curtain lining the space, striped with an abstract landscape of brown, green and blue bands – a gloriously 70s vision that would have made the young Terence Conran proud. Doubling up as a cinema and events space, the walls are clad with raw plywood and exposed acoustic foam, set in a grid that echoes the outside, while a big semicircular window provides views out over the rolling Campbell Park, framing the arc of a permanent sunset to the west. The beautiful red spiral fire-escape stairs, sheathed in a cylinder of perforated polished steel, make you long for an emergency drill.

Outside, Norman and Jones’ work continues in the form of a surreal playground (not yet finished) that references some of the famous street furniture of Milton Keynes, taken from the city’s original Infrastructure Pack design manual. With little sunken bollards for leap-frogging, a cluster of climbable lampposts, and a rubberised neolithic tor, it promises to be as whimsical as the original urban planners’ trippy visions of the city as a fantastical leisurescape.

It is part of their wider research project on the City Club, an unrealised plan for a mind-boggling leisure centre at the heart of Milton Keynes, which would have included a souk, wave pool, rodeo and farmers’ market – conceived with an anarchic spirit that has infected the whole gallery. A model and photographs of the epic complex are shown in the opening exhibition, The Lie of the Land, which places the history of Milton Keynes in the wider trajectory of the British landscape, charting how leisure and culture have transformed the land, from Capability Brown’s gardens at Stowe to the utopian ideals of the new towns.

It is an eclectic and intelligent show which, like the architecture of the building, will make you realise that Milton Keynes is worth a closer look.