Tour de force: Nelson has created a puzzling set of rooms inside a familiar British building . Rating:

Tour de force: Nelson has created a puzzling set of rooms inside and imposing building

Just when you start to think the Venice Biennale has become predictable, an artist comes along who does something so unexpected and with such conviction that you never forget the moment you first saw it. It happened to me in 1989 when Hans Haacke took a jackhammer to the floor of the German Pavilion, and again when the Chinese artist Cai Guo-Qiang sailed a Chinese junk down the Grand Canal to perform acupuncture on the city.

The scale and ambition of Mike Nelson’s intervention in the British Pavilion would take away the breath of anyone who sees it. But for those who know the building well, the pleasure of the work is increased tenfold – for it’s as though Nelson has torn down a cosily familiar and quintessentially British landmark and replaced it with a series of rooms you’d expect to find in the back streets of Venice or the slums of Istanbul.

These are incredibly unpleasant places in which to spend any time – with harsh neon lighting, dirty mattresses and blankets on the floors, rags covering television sets that are never turned off, empty petrol tins, broken furniture and rusty tools lying on wooden tables – everything speaks of dirt, re-use and hopelessness. If there is such a thing as moral beauty, then this, I’m afraid, is its opposite.

In fact, what he’s done is to create a building within a building using cheap materials, salvage and objects he found in skips and junkyards in Venice and Istanbul. Blocking out the real doors and windows that would help visitors to orient themselves within the space, Nelson sends us on a journey through rooms that most of us would not and could not see – places poor artisans, migrants and political zealots might inhabit and which we “read” differently depending on whether we consider one space more “Muslim” than another.

Nelson likes to play tricks – we wander without a compass through these spaces and instantly get lost. A courtyard open to the sky and with an external staircase rising two stories upwards could be a house in either Venice or Turkey – but the joke is that we are standing in the centre of the “old” British Pavilion. How did he do it? He simply removed the roof.