The City Observatory on Calton Hill was a decrepit ruin until arts group Collective decided to make it their spectacular new gallery, giving new life to a monument to the Scottish Enlightenment

Edinburgh’s old and elegant skyline has a thrilling new attraction, a hilltop haven for art lovers and astronomers, dog walkers and coffee drinkers. The City Observatory on Calton Hill spent most of the past century descending into dereliction. In recent years, it has been hidden behind hoardings, letting the pillars, towers and spires elsewhere in the city take all the glory. But now this pretty little neoclassical building can be seen again, its dome glossy, its portico proud, its telescopes lovingly reconditioned.

The restoration of this scientific monument – designed in 1818 by William Henry Playfair – has been led, somewhat improbably, by Collective gallery, a small, not-for-profit visual arts organisation. The last eight years have transformed its director Kate Gray into a seasoned negotiator. Besides raising the £4.5m required, Gray and her team have managed to balance the conflicting demands of an enormous number of bodies: the city council, world heritage groups, architects, construction firms, astronomers, restaurateurs, tourists, revellers and even local dog walkers, not to mention all the artists the gallery supports. “The expectation was that people would see the site and expect the National Galleries,” says Gray. “And that’s really not who we are.”

The City Observatory fell victim to is own research … proving that the heavens were better studied from the clear air of distant mountaintops

With dramatic views in all directions, Calton Hill is a tourist magnet, pulling in around 400,000 visitors annually – but there’s not a lot to do up there once you’ve finished snapping selfies. As a result, footfall for the gallery, its panoramic restaurant and arty shop is hoped to be high. “The challenge,” says Gray, “is going to be keeping our core audience as well as working with the new visitors.”

Just a few decades after its inauguration, the City Observatory fell victim to its own research. Studies by the second astronomer royal, Charles Piazzi Smyth, demonstrated that the heavens were better studied from the clear air of distant mountaintops. So in 1896, the Royal Observatory moved out to Blackford Hill. Handed over to amateur astronomers, who lacked the funds to maintain it, Playfair’s building was vandalised, the lead stolen from its roof, while water and rot slowly destroyed its interior. The last astronomers left in 2009.

Facebook Twitter Pinterest Enlightenment … the view across Edinburgh from Calton Hill. Photograph: Murdo MacLeod/The Guardian

The walled hilltop site is home to four generations of observatory: besides Playfair’s main temple-like building, there’s a gothic-towered structure, a little transit house used by astronomers before the completion of Playfair’s creation, and the brick-walled rotunda known as the City Dome. None are capacious. With the telescopes still in situ, all that could be used of Playfair’s observatory was a small library to the back, with a little shop tucked alongside the telescopes. The new Hillside gallery and office, meanwhile, had to be dug discreetly beneath. “The site looks very grand but it’s a domestic scale space,” says Gray. “There are no big buildings – they were built for one or two people.”

Collective first became involved in 2010. The council had been warning the gallery it could lose the city centre space it had occupied for 20 years. At around the same time, Collective gave its support to some artists who were staging a video installation at the City Dome. “The more we researched the site,” says Gray, “the more interesting it became for a visual arts organisation.”

Significantly, the observatory complex was held in what’s known as the Common Good – meaning that, while the council was responsible for the buildings, it could neither sell them off nor loan them to any private organisation that might render the site inaccessible.

There hadn't been a new building put up here since 1892. When you have a site with amazing views on all sides, there's nowhere to hide anything

For the council, the appeal for rehousing Collective up on Calton Hill was twofold: not only would it bring public purpose to some important buildings left derelict, it would also allow the gallery to become more self-sustaining. Its old shopfront site on Cockburn Street was flanked with cafes, bars and gift shops: there wasn’t much scope to get in on the game. On Calton Hill, however, there’s nothing but strange monuments and a great view. Collective’s new restaurant, coffee kiosk, shop and event spaces will all help to raise funds.

For five of the eight years of the transformation, the gallery based itself in two portable huts on site. “We felt we needed to understand the hill better,” says Gray. “So we moved up. We learned lots: who comes up, what they were looking for. It was pretty much split between dog walkers and tourists. They all said they wanted two things: a cafe and toilets.”

Facebook Twitter Pinterest The hill is made of basalt, which makes it difficult to excavate. Photograph: Murdo MacLeod/The Guardian

Easier said than done. “There hadn’t been a new building put up here since 1892,” says Emma Fairhurst, the project’s architect. “It’s 40 metres above street level and the hill is made of basalt, which is very hard to excavate. And the visibility of the site was a huge challenge in terms of planning: when you have a site with amazing views in all directions, there’s nowhere to hide anything.”

The observatory building was, she adds, “in a sorry state”. The interior had to be stripped back to the stonework, but the saving grace for the conservation team was a set of Playfair’s original drawings. “Many of the details are drawn at 1:1 or 1:2.” That’s full-size and half-size. “Playfair was really meticulous,” she explains, “which was great for us.”

Facebook Twitter Pinterest Seeing stars: the main telescope has been refurbished. Photograph: Murdo MacLeod/The Guardian

Integral to the design is a pair of transit slots, or viewing windows, that slice right through the building on a north-to-south axis. When the Observatory was designed, “astronomy was all about timings and marking exact positions”, explains Andy Lawrence, Regius professor of astronomy at the University of Edinburgh. From 1853, a “time ball” was dropped down the adjacent Nelson Monument at precisely one o’clock: it could be seen through telescopes used by navy vessels in Leith docks. In 1861, what was then “the longest wire in the world” stretched from the Observatory to Edinburgh Castle, setting off the city’s famous one o’clock gun.

Such precise timekeeping was, for a brief period, globally significant, says Lawrence, because of the role it played in navigation and, by extension, the boost it gave Britain’s sea power. “But you can also see it as part of an overall 19th-century obsession with precise measurements,” he says. “It was significant not just for sailors but also for railways. Getting accurate time and unifying it was important for civic infrastructure across Europe.”

The site’s rich history has provided plenty of inspiration for the opening exhibitions. A complex installation by Dineo Seshee Bopape in the City Dome explores alternative cosmologies and methods of prediction. The library houses drawings and diaries by James Hutchinson, inspired by two female scientists with close links to the building. Klaus Weber’s cheeky sculpture Nonument, meanwhile, suggests an inglorious addition to Calton Hill’s neoclassical lineup: a cigarette-smoking snowman wearing a broken bottle for a hat.

Facebook Twitter Pinterest Alternative cosmologies … Dineo Seshee Bopape’s installation 〰️ [when spirituality was a baby] in the City Dome. Photograph: Murdo MacLeod/The Guardian

“It’s a real shrine to the Scottish Enlightenment up here,” says Frank Little of the council’s culture department, “but we never wanted to preserve it in aspic. The Playfair building in its time was cutting edge, but it has to have a purpose and a future. The Enlightenment was about inquiry and intellectual pursuit. Working with Collective is genuinely exciting: it gives it a completely contemporary focus.”

Facebook Twitter Pinterest Klaus Weber’s Nonument to contemporary Edinburgh in the complex’s Hillside purpose-built exhibition space. Photograph: Murdo MacLeod/The Guardian

These have been tough times for arts funding in Scotland, and there has been some ugly fallout over the recent closure of the gallery at Inverleith House. Collective’s arrival at the top of the hill seems part of a new blossoming. Earlier this year, Ingleby Gallery relocated to the atmospheric Glasite Meeting House, while the venerable Fruitmarket Gallery is also poised to expand.

It’s not just good news for art-lovers. Lawrence says Edinburgh’s astronomers are “enormously pleased” that Collective has taken over the Observatory. “The idea of someone caring for it is really nice,” he says. “In the 19th century, great things happened here. But for the latter half of the 20th century, the place was slowly rotting away. Kate’s a miracle worker for pulling this off.”