Miroslav Balka at the Tate Modern

It's all about the moment you have to walk forward. A gaping metal gangway up into a large rusty metal container, which echoes unnaturally dully. Only dim, pale shapes that do not appear as people are visible in the gloom. As you move forward, the motion of the shapes begins to resemble the hesitant rise-and-fall of walking. Sounds are faint and fuzzy at the edges. The slightly more confident shuffle of people emerging from the darkness is a reproach, a challenge to have to guts to step forwards into a profoundly unpredictable and unknowable place. Like all the best of the Unilever Commissions at the Tate Mod, it works by radically redefining the space of the Turbine Hall, rather than by trying to fill the space with new material. Its a genuinely disturbing moment, best experienced alone.