A 68-ft pineapple does not grow out of a basket perched on top of St. Paul's Cathedral. Sir Robert Peel does not rise from the middle of the Thames at Vauxhall. Pyramids destined for Trafalgar Square and Shooters Hill have been sent about their business. A Crystal Tower Bridge, an Eiffel Tower at Wembley and a Roman Colosseum at the top of Whitehall are among the many bizarre schemes that have enjoyed brief, giddy moments of acclaim and then, having strutted their hour, are heard no more.From public archives, private collections and the Royal Library at Windsor the authors have unearthed projects for London conceived during the last 400 years. Included in this richly illustrated book are prodigious palaces and pleasure domes, such as one wistfully studied by Charles I in prison and another optimistically envisaged for Hyde Park by the Old Pretender while in Italian exile.Sometimes, projects were not built because they were not meant to be taken seriously, but such fantasies should not obscure the many imaginative proposals by architects genuinely dedicated to London's improvement. In the 19th century, for example, rival architects fought -- sometimes none too scrupulously -- to win competitions for important buildings. The battles waged by such Victorian giants as Charles Barry, Gilbert Scott and Alfred Waterhouse make dramatic and fascinating reading, as do efforts to bring about change by such controversial 20th century figures as Patrick Abercrombie, William Holford and Norman Foster.The London that might have been is full of variety and the unexpected.