It's not often we can drag the cool set over to gritty south London, but they're queuing round the block to experience British artist Roger Hiorns's crystallised flat.

Just north of Elephant and Castle, in an unlikely housing estate, something beautiful and deadly is blooming.

At first, the brutalist courtyard with boarded-up buildings doesn't look too promising.

But as you get nearer, you spot a group of fashionable young things exchanging their shoes for wellington boots and gloves.

Entry to the flat is on a first come, first serve basis. Admission is free.

You don't quite know what to expect as you cross the threshold of the dilapidated flat.

But turn right and the blue hits you like a physical shock.

Hiorns has filled a bedsitter with 90,000 litres of copper sulphate solution to create a "total crystallisation".

The liquid was poured through a hole in the ceiling into a huge sealed tank.

After a few weeks the temperature of the solution fell, excess liquid was pumped out and the crystals began to grow.

Finally the tank was cut away.

The skeleton of the flat is still visible: walls, ceiling and all the bathroom fittings (including a ghostly bath covered in viciouslooking blue stalactites).

Watch out as you crunch over the hardened sludge of crystals: some dense, glass-like shards are at least several inches long.

The piece was commissioned by Artangel (who brought us Rachel Whiteread's House) and the Jerwood Charitable Foundation in association with the National Lottery, Arts Council England and Channel 4.

It continues Artangel's long tradition of transforming urban housing into large-scale immersive works of art.

Hiorns is known for working with unusual materials, having previously created works with detergent, disinfectant, even his own semen.

And he loves the idea of a solid mass taking over a space which was once someone's home.

Part chemistry lesson, part urban intervention, there is something terrifying about Seizure (until the poisonous liquid turns into crystal, it is toxic).

You emerge into the sunshine sweating slightly despite the cool temperature in the grotto.

After the exhibition is over, the rundown modernist housing block will be demolished.

But it will stay in your mind for ever.

Tues-Sat, noon-7pm. Until 2 November. Information: www.artangel.org.uk