Masterpieces in the mind's eye

We asked readers to let their imaginations run free and submit proposals for buildings they would like to see erected with Millennium money - unfulfilled designs, great structures of the past, or even the frankly fantastical. Jonathan Glancey applauds the ideas on show

Zaha Hadid's Cardiff Bay Opera House topped your list of scuppered or otherwise unbuilt architectural masterpieces you dream of seeing built for the Millennium with Lottery money. I asked for your suggestions three weeks ago and you responded fulsomely. "Cardiff Bay Opera House, of course", summed up 14 readers' feelings about a striking adventure in contemporary architecture that would have been built, unquestionably, should it have been proposed in Germany, France or Spain, but in Wales, a country not famed for its architecture, was consigned to the creative dustbin.

One can almost imagine Zaha Hadid - a dark, foreign woman (Iraqi-born and an intellectual to boot) being tied to the stake and burned to death while the boyos, bolstered by beery and biblical bravado, stood by and jeered. Architects of any calibre will steer well clear of Cardiff in future.

Hadid's design was, without doubt, challenging, but potentially very beautiful and a building that would have attracted global attention and brought the world's greatest opera companies beating at its Deconstructivist doors.

Another modern masterpiece consigned to the dustbin that several of you chose was Foster Associates' design for the rebuilding of Hammersmith Broadway. This remarkable hi-tech scheme would have transformed this ill- formed and immensely busy west London junction into one of the most imaginative edge-of-town centres in the world. Combining bus and Underground stations, shops, offices, a covered public square and representing Norman Foster at his very best, the loss of this project in the late Seventies was a sad one. Even sadder was the fact that when the extensive Hammersmith site was redeveloped in the early Nineties, what arose was the sort of big, bland post-Modern block better suited to an edge city shopping mall in the heart of New Jersey than to one of London's principal western gateways.

The most forward-looking votes of all, however, went to a "British wing of the forthcoming European Space Station" and to a recreation of the wonderful space station that played a starring role in Stanley Kubrick's epic film, 2001: A Space Odyssey. Richard Allen of Edinburgh suggested the former. Mildly condemning my suggestion of building Lutyens' design for Liverpool Cathedral and Wren's Greek Cross design for St Paul's, ("magnificent in their time ... but would not reflect current thinking"), Mr Allen believes the European Space Station "would be a true cathedral for the scientific culture of the 21st century."

Lucy Manners of Norwich chose the space station from 2001 - designed by British special effects experts - because "it is more beautiful than almost any modern building, a cross between jewellery - a great bracelet among the stars - and high technology. It would be a place where representatives of all nations would meet and work together as they looked to the future".

Peter Forster of London is another fan of Lutyens' Liverpool Cathedral, but believes that it would be a "monstrous white elephant today ... a colossal monument to the irresponsibility and irrelevance of religion today." Nevertheless, Mr Forster would like money spent on a full restoration of the great model of the design currently in the care of the Walker Art Gallery, Liverpool, which has been trying to raise funds for this purpose. When the model was shown at the Hayward Gallery's "Lutyens" exhibition in 1981, it had clearly lost many of its detailed features: "someone up north", suggests Mr Forster, "must have a fabulous model railway trundling among Wrenaissance towers and spires."

Mr Forster adds that he would like to see the Euston Arch (1837), the Crystal Palace (1851) and the Skylon (1951) rebuilt. Plans for the first of these (the original was demolished with the cynical consent of Harold MacMillan, then Conservative prime minister, in 1962) are under steam (see Eyecatcher opposite) and the other two are often mentioned as buildings many people would like to see resurrected.

AR Wilson (no address given) wants to engage in a bit more demolition work in order to see his favourite unbuilt design realised. "Why not demolish the Houses of Parliament," writes Wilson, "and rebuild them to the design of Sir John Soane, the drawings of which can be seen in the Soane Museum in Lincoln's Inn Fields?" It is an interesting idea. Soane's design was, as one might expect, imaginative and possibly magnificent.

My own view is that Barry and Pugin's Neo-Gothic folly succeeds brilliantly with its thrilling skyline which, along with the dome of St Paul's cathedral, has become a symbol of British democracy and defiance in the face of foreign tyranny. The Luftwaffe had a go at destroying the great Gothic palace during the Blitz (it took out the House of Commons, which was later rebuilt by Sir Giles Gilbert Scott), but if those who occupy it have little or no place in our hearts, this fairytale building does.

More demolition work is suggested by Michael Walker of Lowestoft. He wants, perhaps even more controversially, to rewrite history by spending Lottery money on removing the Catholic cathedral from the centre of the great mosque (or Mezquita) in Cordoba and rebuilding the roof and arched colonnades needed to bring this magnificent Islamic prayer hall back to its orginal state. "It is quite the most beautiful building I have ever seen and the incorporation of the cathedral at a later date was an act of unparalelled vandalism." The project is not in the United Kingdom, as Mr Walker is the first to remind us, but he says, "What a magnificent gesture it would be, showing our commitment to the European ideal and reaching out beyond to the Arab people."

This is an absolutist view of architectural history and I think although it would be wonderful to see the Mezquita as it was in the days of Cordoba's most exquisite flowering, the demolition of the cathedral would be an act of barbarism today. It is very often the meeting between such buildings of different eras and cultures that thrills the architectural tourist. However, in fairness to Mr Walker, few people would want to return the Parthenon to the state in which it featured a Turkish mosque inside its famous Doric colonnades. Because the mosque was used as a store for gunpowder, the most famous and influential of all ancient buildings was wrecked by a massive explosion. Equally, few people would agree to restoring the Parthenon to its original state. To our eyes, trained to see it as a chaste and geometrically pure monument, it would be a shock to see it gleaming in its original colours (even more of a shock, of course, if the British Museum were coerced into handing back the Parthenon's peerless frieze which we know as the Elgin Marbles).

My favourite of your letters (there were 78 of them) was from Michael Quinn of Caversham, Berkshire, who hit the nail on the head when he wrote of the three buildings by Hawksmoor, Lutyens and Wren that I would like to see standing (but, with the exception of Hawksmoor's piazza for St Paul's, probably only in post-camembert dreams), "these buildings, though never built, actually exist in the same way that a piece of music exists as a score even if never played; perhaps they deserve a 'performance'". But, adds, Mr Quinn, we should put our efforts into a building of our own times that would be the "glory of this age, built just for once regardless of petty squabbles over cost, and one which would match any of the greatest of past buildings in expressing the spirit of its age." Mr Quinn would site this building at Greenwich. "The only trouble," he says, "is can we rise to the occasion - do we have any greatness to express?"

Where there has been greatness, however, we ought to be aware of it. A truly great architecture exhibition for the Millennium would be one in which the sublime monuments our architects designed, yet we chose not to build, from Wren's Greek Cross temple to Zaha Hadid's Welsh opera house, were put on display in a way in which we could get some feel of how they would have appeared in reality. Such buildings may be the stuff of dreams, but when we block out our fantasies and let boyos and bucks, parsimony and the pound rule every decision we make about buildings, we also deny ourselves the possibility of future Wrens and Hawksmoors, Lutyenses and Soanes, and, worse, fail to acknowledge the talents under our millennial noses.