You can't quite believe what you're seeing. On the Sadler's Wells stage two men with the insouciant swagger of Jay Kay are throwing stones at each other.

Well, not exactly stones, more like breeze blocks. They hurl them at full force across the stage, the thrust and effort visible in the throw, and the force of momentum clear in the catch.

It's genuinely risky, a risk doubled when the bricks almost scalp the heads of female dancers who are ferociously running by.

It's often said that Wim Vandekeybus brings real danger to the stage, pushing his dancers to their physical limits, having them strain and fall, and then duck incoming house bricks, then run a relay race with them, then throw them randomly across the stage for anyone, anywhere to catch.

This combat-as-choreography approach was thrillingly, unsettlingly clear during the 90-minute Spiegel, a retrospective of Ultima Vez excerpts from the past 20 years.

Clearer still was his ingenuity and humour, both of which you easily forget amid his choreographic battlefield.

Who would think of choreographing with bricks? Who would think of following it with a dancer gently blowing a tiny white feather across the stage, never letting its gossamer fronds tickle the floor.

The improbability of the elements, the weight and float, the contrast and release, remind you that Vandekeybus is not only showing how the body moves, but how the heart leaps.

Wim Vandekeybus was part of the Flemish New Wave in the 1980s that abandoned the academic refinements of modern dance and gave us the nonchalance of skateboarders and the impact of military assault.

This, and the bed-sit chic, is not everyone's cup of tea, but Spiegel (meaning "mirror") reveals the energy and strength of the body, as well as its gentleness, and the inherent mystery of it being our home.