Architecture: Light, air and PVC

The islands in Alan Parkinson's Archipelago are so entrancing that visitors lie down, curl up and meditate, but they're not allowed to bounce.

This evening, a three-day wonder of an inflatable building called Archipelago on Canary Wharf Plaza in London will have its tent flaps unzipped and will subside in a great gasp. The four cubic metres of PVC will be loaded on to a truck and driven to its next destination. Its creator, Alan Parkinson, calls his installations "ephemeral architecture" and in his studios in Nottingham and Geneva mostly makes inflatable structures for theatre workshops. One is on tour in Germany, currently playing to crowds of 3,000 a day in Dresden. Another is at Ross-on-Wye festival. Pray that winds don't gust at more than 40 miles an hour this Bank Holiday weekend or the whole thing will end up in Brittany. Mr Parkinson has given instructions to pull out the bung if the wind gets up.

Archipelago is anchored with concrete slabs on the forecourt of Norman Foster's new Jubilee Line Extension station at Canary Wharf. It had been hoped that the inflation of this 1,000-square-metre installation would coincide with the opening of the station but delays have meant we now have to wait another three weeks for the latest chapter in the Fosterisation of London. London Underground even paid half the pounds 40,000 costs for Archipelago, sharing them with Canary Wharf Arts and Events summer programme. Too functional to be sculpture, too structural to be performance art, Mr Parkinson calls his installation a "luminarium" since inside its colonnaded malls and eight-metre high domed halls, all cushioned in red, blue and green pressurised PVC, is a sound and light show. His manipulation of light and space makes boundaries blur like light artist James Turrell's gallery installations. And his works are accompanied by health warnings - people can become disoriented.

It may look like a kids' bouncy castle from the outside but visitors are discouraged from larking around once inside the airlock. The awesome, cavernous halls in psychedelic colours have inspired some very untypical British behaviour. Barefoot visitors - spiked heels would puncture the PVC - stretch out their hands to touch both sides of padded niches which pout like Mick Jagger's lips. People lie down, curl up, meditate and do yoga.

Flotation tank music plays softly to drown the sound of the 10 fans which blow 1,000 cubic feet of air a minute into the structure, powered by as much electricity as it takes to run two kettles all day. The gaudy PVC is specially coated to meet fire regulations and illuminated purely by daylight through slivers of transparent plastic windows. It glows like stained glass, an effect that the designer describes as "a phenomenon of radiant light and colour, such as you experience in a cathedral, providing the same kind of stimulation, or peace." The main chamber has a hexagonal colonnade and Arabic muquarnas stained-glass patterns above. Another hall is pierced high overhead with transparent indigo seals in a pattern as elaborate as Quetzacoatl's head-dress. This is where Moorish meets Aztec.

Mr Parkinson sees himself as a structural engineer working in soft materials rather than concrete, steel and glass. He even uses a welder's sheet-metal manual to help him cut the template like a dressmaker after drawing his designs by hand: "I've no time for a complicated computer learning curve," he admits. He describes Archipelago's domes as "truncated icosidodecahedrons" (32-sided object), a reference to the complex geometry of Antoni Gaudi, Barcelona's most famous architect, who learned about complex membrane surfaces by watching his father, a metalworker, beat and curve and stretch flat metal sheets. Hyperboloids, helicoids and conoids are all constructed from the basic cones, spheres and cylinders that Mr Parkinson welds together.

Sometimes he pleats the plastic, and by altering the tension in the pressurised PVC, he can softly contour great concave scoops out of domed ceilings. Slashing diagonals into one chamber's opaque surface and filling them with transparent PVC, he achieves a lattice-like diamond pane effect (although it bathes the yellow chamber in a golden glow, he won't admit that it's like stepping inside a Lava lamp).

"I haven't got lost in it yet but I know people who have." Mr Parkinson says. Which is why ticket holders on the half-hourly tour get a colour- coded map. Norman Foster, who hates to be labelled a high-tech architect, often citing the fact that he admires Gaudi's organic qualities most of all, would approve of this crazy pleasure dome but alas, by the time the guided tour of his Jubilee Line station takes place, Archipelago will have gone. That's ephemeral architecture for you.

Tours every half hour of `Archipelago' 11am-5pm today, tickets pounds 3.50 for adults, pounds 2.50 for under 16s (must be accompanied) and pounds 10 for a family ticket, under 5s free.

`Archipelago' is fully accessible by wheelchair