Beyond, caverns beckon, the darkness lit in pools

Entering from the street, you're at once in medias res. A period dining-room by candlelight is where you find yourself, set for some select society, esoteric perhaps, or imperial, for there are two sphinxes on the table - and around them, all the signs of a banquet abandoned mid- mouthful. There's distant music and a strong scent of oranges, but you only have a moment to take in this scene, which looks so rich in evidence. A door at the far end opens. An usher appears and firmly ushes you through. As you go, you pass a side table, an old copy of the Times placed on it, dated Thursday 12 September 1895, and a liqueur glass engraved with the monogram HG. Beyond, caverns beckon, the darkness lit in pools and flashes.

HG is the name of an installation work on an epic scale constructed in the Clink Street Vaults - the vaults of the original "Clink", the medieval prison in Southwark, now the property of Railtrack. It's the creation of Robert Wilson (visionary man of the theatre), Hans Peter Kuhn (artist in sound and light) and Michael Howells (Peter Greenaway's art director). It's very, very big.

But should you wonder for a start what HG stands for, and the letters recur like clues on various objects throughout the show, the answer is: HG Wells, or rather, HG Wells if you insist - but it was nicer when you were just wondering. Yes, The Time Machine was published in 1895, and HG offers (kind of) a journey through time. But the references aren't specific. Like its title, the whole work maintains an air of not quite resolved enigma.

The first few chambers spring a mouth-opening series of visual and imaginative coups. A flashing spotlight sweeps violently to and fro among pillars, a (stuffed) cat lurking among them. Move on: a remote space glowing an unearthly blue draws you toward it. A barrier stops you. Is the human silhouette in the middle distance alive? Turn back: a mummified figure catches your eye, sharply picked on the floor, a lone sleeper under a huge and gloomy dome. High above it, caught in another beam, an arm hangs in mid-air.

Round a corner, and a wide, low-ceilinged area opens, filled with row on row of hospital beds, each neatly made, each lit by a weak naked bulb. Move between them; shafts sunk in the floor hold buckets of gouty blood, and from traps in the roof, printed matter cascades down as if from some overflowing archive. Peer through a grille in the wall and you see far off, beyond another gloomy chamber, a luxuriant and leafy arbour, a, glade apparently growing greenly underground. Everywhere you look, it seems some tableau or vision is waiting, and always something more, just out of clear sight.

If you've ever been to an art-installation and thought, This could have been made a bit more theatrical, a bit more amazing - then HG is your wish answered. Installation work generally holds back from sheer spectacle (we should reflect on what we're looking at, not gawp and gasp). Even with a will, it can rarely compete with big-time displays of stage, screen and theme park. HG knows no such constrictions.

It has the resources: a really extraordinary amount of space to play with, subterranean darkness to be illuminated, an architecture offering numerous openings, hollows, grilles, passages, expanses - a setting in which almost anything would look numinous. It has the money to indulge: each one of its inventions would be enough to constitute a good-sized exhibition. It has no scruples at all about being spectacular or voyeuristic. HG revels in the many modes of looking, through peep-holes, on to sudden vistas, into hidden cavities, in fleeting glimpses, across unapproachable distances.

More than a spectacle - an experience you're inside. You might think of ghost-trains, dreamscapes, CD-Rom discovery games, magic toyshops, fantasy environments, a virtual headset made real. There's room to explore, to be disoriented, illuded, surprised, truly mystified - and for a range of sound effects to be deployed without mutual interference. It's full of noises. A favourite trick: the music sounds distant when the sound- source is close, implying an untraceable elsewhere. That's HG all over, the sense of something revealed and not fully revealed, something just beyond you (your senses, your understanding), the very model of a mystery.

About half-way through, after the first relay of amazement, you may start to have doubts. It was in the space where water dripped from the ceiling and the floor was littered with "old master" portraits covered in dust and cobwebs, plus a large garden gnome and a small Christmas tree, that (for me) the illusion cracked. Surely, a parody of an art-movie set, a farrago of blatantly suggestive devices. Then these doubts begin to pervade.

For aren't we just going through a menu of shows, an illusionist's portfolio, one stop pulled out after another? And isn't HG's emotional repertoire a matter of very bold primaries, knee-jerk atmospherics? It deals in responses that are powerful and immediate, but familiar - because they're familiar. The abandoned meal, the corpse in the catacomb, the scary searchlight, sinister hospital, secret garden: we've been here before, this land of the imagination is well trekked. And is this trail of mystery leading anywhere?

Ghost-trains are quick, for good reason. When you have time to wander, you have time to ponder too. Sheer spectacle as such exhausts itself. There's a difference between discoveries you make yourself, and discoveries that are made for you. You have to ask: made for us why? Something vaguely to do with the past is the idea, I guess, vaguely to do with London, ancient centre of wealth and power, the Empire's lumber room, city of plague and horrors; not so far in fact from touristic London - the London Dungeon is just a walk away - history as haunted house. HG certainly doesn't reflect concretely or specifically on its site. The history of the Clink only supplies an extra aura of the macabre.

As these thoughts settle, HG's most beautiful and strange creation strikes: through a high arch, a seemingly infinite expanse of ultramarine, and floating in the sky a hundred arrows suspended in flight - after that, nothing so wonderful. Galleries filled to brimming with used cans and cups, a croc's head poking out of them for added weirdness. A floor dotted with many miscellaneous pairs of shoes (this device is by now an installation cliche). Lots of glowing objects and substances. A large and very tacky plaster sphinx, bright-lit behind a half open door.

HG gets to feel made up as it went along (what shall we do with this space?), and to feel as though time or invention were running out when they approached the end: another cave to fill, thousands more cubic feet to dramatise, and with all its intimations of meaningfulness - no guiding idea or story to give it final shape. The last vault is vast and void but for a white bunny, again mid-air. Alice's guide? The conjurer's confession?

Well, I feel torn. HG's promiscuous, prodigal will to beguile and amaze is admirable, and the standard installation rule about "responding to the history of the site" has become a reflex piety. Why not just use the site for all its worth? But HG also asks its visitors to lose themselves in the immediacy of its experiences. Take this open-ended sequence of mysteries at face value, don't reflect - or rather, reflect just enough to be drawn into a promising quest, but not so much as to find the trail false. In short, it's a work of pure suspense, and even if you stayed up with it all the way, you're likely to come down later with a bump.

n `HG' is at the Clink Street Vaults, London (0171-336 6803) to 15 October

exit poll

What the public make of `HG'

"What I think will stay with me are individual scenes - like the first room [a Victorian dining-room] which has been abandoned in the middle of a meal like the Marie Celeste - rather than any overall impression. Don't ask me what it's got to do with HG Wells, but it was fun."

Jacqueline Hart, 62, Hampstead

"I suspect HG Wells would find it pretty hard to find any link between the ideas he was interested in and this. He's probably spinning in his grave as we speak."

Trevor Mason, 36, Hammersmith

"I loved it. My favourite bit was the rain forest you can only see through a barred-up window. The bars are so close together that you can only see through them if you tilt your head at right angles, and even then all the plants seem so far away. I thought that was a really sad image."

Rachel Moore, 28, Southwark

"I wish there had been more of a story to follow. I found it impossible to make connections between all the different objects, like the Sphinx and the hospital ward for people with flu. And what was that garden gnome doing in the middle of it all?"

Tim Moorby, 26, Clapham

"I think it's stupid to complain that there's no story. To me, it's very clearly about how all societies, whether they're Egyptian or Victorian or modern, are so fragile. You're meant to feel you're wandering around the relics of all these civilisations, so of course it's going to feel a bit disjointed."

Peter Dunn, 34, Edinburgh

"The vaults are so atmospheric anyway that I don't think the people who put on the exhibition could fail to make it seem spooky. It's almost too easy."

Jane Bosick, 42, Southwark

"I liked the man who looked like a mummy and the drains with blood in them".

Mark Kidd, 11, Balham

Interviews by Adrian Turpin