Mass culture. Intelligent architecture. Thoughtful urban design. These three elements rarely coalesce. In fact, it is probably fair to say that the architecture of mass entertainment reached its zenith when it first began, with Joseph Paxton's peerless Crystal Palace built to house the Great Exhibition of 1851. One in three of the adult population of Britain visited Paxton's masterpiece and the memory of this superb structure has gone on to inform the work of some of the most adventurous architects of recent years. Ever since the Great Exhibition, there has been a tendency for the architecture of mass entertainment to branch away from that of high culture or basic good manners. Perhaps the closest a single building has got in recent years to closing the gap between mass culture (or at least mass movement), intelligent architecture and thoughtful urban design is Nicholas Grimshaw's Waterloo International Terminal, where those prognathous Eurostar trains bask under the architect's snaking blue steel roof.

Now, a stone's throw (should such a thing be allowed with so much glass around) from Waterloo International comes another building that performs the same balancing act. This is the London IMAX cinema designed by Bryan Avery which opens to the public on May 1. Commuters in their thousands have watched Avery's 100-ft tall steel and glass cylinder rise from what was for many years Cardboard City, an extensive rag-and-bone home to a hardcore of London's homeless. Cardboard City occupied the undercrofts of the extensive realm of concrete passageways that were designed to connect the various parts of London's South Bank cultural complex to Waterloo station itself. The new IMAX cinema (the third to arrive in London) springs from the roundabout that was the sad and dismal hub of these important pedestrian routes. Many people, feeling threatened, were too scared to use them. With the arrival of the London IMAX, they will no longer feel that way. Whether IMAX (Image Maximum) films are to your taste or not - giant 70mm affairs, some in 3-D designed to make audiences feel they really are in the heart of a rainforest, in the Oatesian depths of Antarctica, on stage with the Rolling Stones or scaling the heights of Everest - anyone who comes this way from next month is likely to be impressed with the job Avery and his team of consultants have done, in transforming Cardboard City into what the architect likes to call an "urban odyssey". The IMAX cinema is the highpoint of this important exercise in urban regeneration, yet the passageways that lead to it and the space that surrounds it promise to be a delight. This might be hard to believe - because they have been so horrid in most people's eyes for so very long - yet Avery has teamed up with artists and horticulturists to create what should prove to be some unexpectedly enjoyable underground walks.

Ron Hazledon, an artist well known for his light installations, is, for example, lining one concrete passageway wall with a grid of blue LED lights, which will cast an ethereal glow along the walk from Waterloo Bridge to Waterloo Station via the IMAX. This passage, one of several, all of them to be made over by artists, leads into the roundabout space itself. In a few months from now the whole of this space will be shaded by a parasol of plants trailing along high-tensile steel cables set between the parapet of the roundabout and the second floor of the IMAX. The harsh sunlight, rain, traffic noise and, to a degree, diesel and petrol fumes will be filtered out by the gentlest vault of ivy, wisteria, jasmine, clematis, honeysuckle and virginia creeper, while, from the ground, snowdrops, sky blue scilla and iridescent Spanish bluebells will play a game of mix'n'match with the sky. The IMAX itself serves two distinct roles, one old-fashioned, one bang up-to-date. It is both an "eyecatcher", as in a folly set in a landscaped garden and a whizzy new place of high-tech entertainment. In design terms, it performs the simple and pleasurable role of providing a modern monument to catch the eye of people travelling south over Waterloo Bridge. Giant artworks, beginning with a painting by Howard Hodgkin enlarged a hundred times and mounted on a 15-metre high "image wall" in the glass gallery that surrounds the IMAX auditorium, will face passengers riding the top decks of London buses. So, again, the world of mass entertainment is linked to that of the wised-up culture presented in the galleries and auditoriums of the South Bank.

The IMAX is a simple building that has taken great ingenuity to build. Composed of a steel and glass drum surrounding a concrete auditorium, it rises above the Waterloo and City underground railway and is thus hemmed in, above, on all sides and below by vibration and noise. To keep these at bay, the cinema is raised on concrete columns topped with hydraulic dampers, or "springs", that soften the rumbles of the underground railway lines and defuse the rattle of taxis and buses, the thrumming of mainline trains and the screech of motorbikes.

Inside the cinema, raised above the entrance lobby, bookshop and cafe, it is unbelievably quiet. In this vast, acoustically dead space (clap your hands and there is no reverberation ), 14 tiers of comfy blue armchairs - 482 in all - rise up to a projection room high above. It is a daunting place, rather like being inside a gasometer. You enter immediately in front of the screen which towers higher than five double-deckers placed one above the other, find your seat and settle back to gawp at the largest cinema screen in Britain. UNTIL Disney and the likes of Steven Spielberg (the former is working on Fantasia 2000 for IMAX screens; the latter is said to be interested) get to grips with IMAX technology, the kind of films you'll see will be spectacular enough, but a bit obvious and no real match for the intelligence of Avery's architecture and urban planning. As the films live up to their surroundings, so the worlds of mass culture, intelligent buildings and pleasurable urban design will have grown up together.

Avery has brought IMAX from the twilight zone of out-of-town shopping centres and leisure developments into the heart of the metropolis. During its first year, half-a-million people are expected to pay to stare up Mick Jagger's nostrils or gaze at the heights of Everest, beneficiaries of the British Film Institute, the Arts Council Lottery Fund (which stumped up three-quarters of the £20 million sterling cost) and the IMAX Corporation of Toronto, which began life in 1970 and has since seen about 200 of its cinemas built in some 25 countries worldwide. Every statistic related to the IMAX business is BIG, yet the joy of this new addition to the London skyscape is that for the first time in many years mass entertainment has not had to spell out dumbing down. And if you're wondering about the fate of all that ivy and honeysuckle exposed to the worst of the capital's pollution, don't worry, an irrigation system will be there to feed them water and nutrients while humans above tuck into buckets of popcorn and tankers of Coke.