In a gargantuan leap of the imagination, Wilkinson Eyre Architects has created Magna, a dynamic adventure in science that rises from the hulk of a decaying Northern steelworks.
Magna is to science what the Tate Modern is to art. Both are bright new lottery-funded visitor attractions that have risen phoenix-like from the huge decayed hulks of heavy industry. Whereas Bankside power station was converted into London's modern art gallery, the Templeborough steelworks between Sheffield and Rotherham has been transformed into a "science adventure centre", due to open over Easter weekend.

By tapping into the potential of science and technology, Magna is that much larger, more powerful and more astonishing than the Tate Modern. The 87-year-old crinkly tin shed of the former steelworks rises to the height of a nine-storey building. Step inside, and you find yourself in a cavernous and gloomy hall in the same gargantuan league as the Tate Modern's turbine hall. After the first gasp of awe, it still takes a minute or so for the unprecedented vastness of this building to sink in. The great hall stretches 350 m in length – so far in either direction that you can barely see the two end walls through the gloom.

Unlike the Tate Modern, the new visitor accommodation is not stacked on conventional floors to one side of the main hall. At Magna, exhibits are housed within four self-contained pavilions that stand within the murky ether of the great hall. The most spectacular of these themed pavilions is a glowing translucent airship that floats beneath the steel sheet roof, tethered by steel guys to the massive existing steel columns.

The four pavilions occupy just a fraction of the giant volume of the hall. Alongside them stand the battered remnants of the steel production plant, including an enormous free-standing arc furnace, where old iron was melted down for recycling. This monster of a furnace, the size of a block of flats and entwined in a Medusa's head of supporting gantries, crucibles, ducts, pipes, cables and ladders, has been retained as a relic of steel-casting production that came to an end in 1993. Even so, Magna is not a steel heritage centre. This had indeed been the original plan launched by Rotherham Metropolitan Borough Council in 1993 with a £50m price-tag. The Millennium Commission offered £22m, but the council was unable to match this funding.

In 1998, the building was transferred to an ad hoc trust, which threw the whole project back into the melting pot and appointed a new project team from the chief executive, Stephen Feber, down – with the exception of project manager Schal.

A career creator of visitor-attractions, including the new Glass Museum in Cheshire, Feber has gone for a slightly cheaper (£37m, recently raised to £46m) but more dynamic concept at the Templeborough works. Instead of looking backwards at a dead industrial process, Feber has planned to use the building as a backdrop for a forward-looking science discovery centre, "where science comes alive". He has limited the subject matter to the four classic physical elements – air, fire, water and earth – and devoted a pavilion to each. The four presentations are real rather than virtual, and have been conceived as "adventures" into the physical phenomena of the elements, many of them encouraging hands-on participation.

Wilkinson Eyre Architects, appointed by Feber on the strength of a competitive interview, shares his dynamic outlook and has added a theatricality of its own. "We've juxtaposed this memorial to a dead industry with new pavilions devoted to new industries," explains Marc Barron, Wilkinson Eyre's project architect. "We've played up the darkness of the space and created a theatrical effect through lighting." The dominant lighting effect, designed by Speirs and Major, is an eerie scarlet glow radiating from the flank wall, where the original metal cladding has been replaced in scarlet glass-fibre profiled sheeting. Inside the gloomy shed, the main structural elements and new pavilions have been picked out in red artificial lighting.

The four pavilions are suspended from the original steel structure, and spur off the original transformer tower in the heart of the great hall, which has been remodelled to contain stairs, lifts, toilets and services risers. The pavilions are stacked in a logical hierarchy, with air below the roof and earth sunk into the basement.

Each pavilion has been designed to express the element presented inside. "The idea is that the architecture is part of the exhibition, and the exhibition is part of the architecture," comments Feber.

This design approach works most spectacularly in the 44 m long zeppelin representing air. It is a classic cigar-shaped membrane, although the traditional canvas skin has been replaced by three layers of translucent ETFE fritted with a film of silver dots. The floating effect is increased by back-projecting films of moving clouds and rippling coloured lights on to the ETFE skin.

Inside the airship, hands-on exhibits designed by Event Communications include a tornado of spinning mist, a field of corn that can be flattened by the gentlest of breaths, and a walk across a replica Tacoma Narrows Bridge as it wobbles to its destruction in a storm. The fire pavilion is closest to a black box; the only external expression is a fiery glow around and below it. Inside, the centrepiece is a 4.5 m high fire tornado, which builds up and subsides, drawing visitors to its heat and glow.

The water pavilion is conceived as "a giant stainless-steel wave", although it more closely resembles Alsop & Störmer's squashed steel tube visitor centre at Cardiff Bay. Its attractions include mists, floods, waves and waterfalls, along with a children's pool and wet play area on the lower floor.

In the basement, the gateway to the earth pavilion is formed by the lifting gear for a giant crucible. A labyrinth of subterranean passageways lead visitors down through piles of earth and slag to a simulated quarry, which they can excavate using real JCB diggers, hoppers, trucks and buckets.

Wilkinson Eyre's dramatic scene-setting begins even before visitors enter the building. Car parking is grouped around a giant slag hopper on the northern side of the shed, and visitors approach the main entrance past eerie banks of artificially created mist.

Inside a large reception hall, visitors are greeted with plumes of smoke produced by dry ice and a multimedia history of the steelworks. They then enter the great hall by a tortuous route that passes through a spooky windowless bunker in raw concrete and up along a new spine gallery.

Feber is delighted that Wilkinson Eyre has achieved its theatrical effects not through mock stage sets but by using materials and forms with a functional honesty in the industrial tradition of the steelworks. Although each pavilion has its own distinctive form and character, one novel material with an obvious affinity to the rusting hulk of the steelworks has been widely used – steel plate that has been artificially rusted and then sealed in clear varnish.

Drawing on lessons from the struggling Earth Centre eight miles to the north-east, Stephen Feber is all too aware that, to succeed, a visitor centre must project a focused message. Magna's four elements of air, fire, water and earth certainly make up such a coherent theme. On the other hand, the relationship of these explorations of the physical world to the hulking old steel mill is at best tenuous, and to younger visitors probably downright baffling. Using Feber's own reasoning, these conflicting messages could undermine the attractiveness of Magna in the eyes of potential visitors, who are expected to flock to this desolate corner of industrial Yorkshire at the rate of 300,000 a year, paying £18 per family for the privilege.

Yet, if Magna's commercial success as a visitor centre is far from assured, its success as a creative piece of architecture is already plain to see. This imaginative fusion of architecture, industrial conservation, exhibition design and lighting plays up the dramatic juxtaposition of old and new to the utmost. That in itself may well turn out to be the biggest draw of the whole attraction.

How Stephen Feber and Schal moved earth, air, fire and water to get Magna built

Magna’s chief executive, Stephen Feber, has managed to conceive, fund, design and build a totally original visitor centre in just two years and one month. When Building visited the site, six weeks before its opening to the public over the Easter weekend, the strains of the rapid development were beginning to show. “The biggest challenge in the entire project has been building it, “ says Feber. “The exhibition industry is used to delivering on time; the building industry is not. There have been constant problems of managing time and cost. We’ve got to have an international quality building, but we’ve already condemned the quality on the toilets twice. For us, coming second is losing.” The man at the receiving end of Feber’s strictures is David Pennells, project manager at Schal. In mid-1998, some nine months before Feber was appointed, Schal won the commission as consultant project manager on the strength of its experience with the Tate Modern conversion in London. After recommending that construction management would be the most appropriate way to procure a state-of-the-art visitor attraction while making good and remodelling the decaying hulk of an old steel shed, Schal also won the commission as construction manager. “Stephen is used to having an existing structure to fit out,” replies Pennells. “Here we’ve had five separate but interlinked pavilions [including the reception hall]. At the Tate Modern, there was a simpler process of stripping out and replacing. But here we’ve had to plonk new things in the old building, so there are constant revisions to the programme. For instance, it took four days to drill a hole through the sloping steel dome in the foundry floor.” Pennells has been responsible for co-ordinating some 80 trade contractors and a maximum workforce of 310 on site. “Some of the artistic exhibition contractors are one-man bands,” he continues. “If you put too much pressure on them, they would just fold. We’ve had to simplify the form of contract for them. What’s more, many of the exhibits, such as the water cannons, have never been done before, so there was trouble in getting them to do the right thing.” When it came to dealing with Wilkinson Eyre Architects, Pennells played a harder game. “It is a highly engineered project, and the architect wanted all this engineering to be made highly visible, which wasn’t so easy. A couple of times, I’ve had to draw a line in the sand and say: ‘Make up your mind or I’ll make it out of papier maché.’ For instance, the architect wanted new stainless-steel members to be fixed to the rusting old steel girders, but this could have caused cathodic reactions. In the end we galvanised the steel.” Several other hidden problems lay in wait for the construction team. “The building had been empty for eight years, and as soon as you moved away from the open door it got very dark, and you could have dropped down a hole in the floor. So the first thing we had to do was put in emergency lighting and safety systems. “When we started demolition we found three types of concealed asbestos, even though there had been three reports saying asbestos was minimal. This meant we had to spend three months stripping out, when no other works could go on inside the building. We also found that some of the columns had grown paper thin with corrosion. So we had to check all the structure and reinforce parts of it. On top of that, 80% of the underground drainage had collapsed, so we had to investigate the drains with CCTV cameras and lay new foul drains in places.” Feber has a double reason to be anxious about completing the building on time. Not only is Magna due to open to the public on 12 April, but just 12 days later it will be officially opened by the Queen. At the time of Building’s visit, Pennells was confident of meeting the deadline.