The question everyone asks of this newest in the Unilever series at Tate Modern is whether or not Muñoz can hope to fill the awesome space that is the Turbine Hall of Tate Modern. I still remember seeing Louise Bourgeois' great towers and feeling that even they were swallowed up by the enormity of Tate Modern's great hall. It was thus with a little trepidation that I approached Bankside to see what Muñoz had in store for us.

For those of you unfamiliar with Muñoz, his work consists of realistically scaled, realistically represented human sculptures. Entering the huge Turbine Hall via the ramp I wondered what to expect. My initial suspicion was that the huge space would be dotted with figures, and that viewing them would be like seeing the trapeze act at a circus. Thankfully Muñoz proved me wrong. Rather, the huge and intimidating emptiness of the Turbine Hall remains just that. Looking up from the ramp provides no glimpse of spider-men scaling the battleship grey walls, no tiny riggers working the aged crane on some last run. It is when one looks down that the fun begins. Beneath the bridge upon which Bourgeois' immense spider tended her young there is a great darkness, stretching off like a burrow. This is Muñoz's masterstroke, and entering into his darkness begins the installation. Even before I laid eyes upon the famous figures, I was moved by the experience. Muñoz has succeeded in doing a great deal with nothing, achieving a mastery of space with what seems to be no effort. The darkness is framed on three sides by the walls of the Turbine Hall itself (Muñoz has added only a roof) and contains very little indeed. The ceiling above is false in two senses: not only is it part of the installation, but it is mesh with piping beyond, just visible. A few dirty striplights do nothing to stave off the shadows. The only real sources of light are the sunlight punching through a number of holes in this ceiling, two of which are occasionally blocked by lifts. Grills and shutters are just visible. For such a large space, the claustrophobic atmosphere is startling.

The lift machinery whirrs, the only noise. These lifts help to emphasise that this underworld has an overworld too, and this is where Muñoz's figures make their debuts. Looking up through some of the "light wells" we become aware that Muñoz has given us, literally, a slice of life. Here are grey men going about their business, some apparently working, some looking down at us, others playing. The first figures I became aware were resting, four in a chain (each sitting on his neighbour's lap) and one perched on a seatless chair. The seatless chair was to prove very important to me, as the work seems to revolve around support, and "what lies beneath". The little vignettes often include doors and passageways leading out of sight, showing a (presumably) ongoing world our rat's eye view cannot perceive. We look up into this grey world, caught for a moment, a neo-Pompeii in wrinkled suits. All the while the motion of the lifts reminds us that there is no single moment, and that we are being afforded a unique view. From down in this industrial Hades the world looks a great deal different.

The underworld is not all of Muñoz's installation however. Returning to the stairs and climbing up to the bridge makes one feels like Orpheus leaving the land of the dead and entering the world of the light and the living. Except there are no living in Muñoz's upworld, just a series of stepped markers, some of which relate to the holes the observer has just looked up through. The grey people are nowhere to be seen. The two lifts climb all the way to the roof, way above the "floor" which stretches to the walls, plying a path between our underworld and the heavens. The whole experience is rather ghostly.

Muñoz's installation poses more questions than it answers — a lot more. The figures remain anonymous and haunting, viewable only from below. The dead machinery of Bankside links the great space with the always-empty lifts, marks of the frozen moment below. The dead machinery of Bankside links the great space with the always-empty lifts. Has Muñoz filled the space? No. Muñoz has done just enough to allow Tate Modern's huge space to fill itself. Looking around the cavernous Turbine Hall I see other people cleaning their shoes, drinking cups of coffee, leading uninterested children. Each is as anonymous as the grey figures forever leading their quiet lives, the next part of their lives just out of shot, unaware that I am looking up at them.