How Trafalgar Square might have looked if an idea for a huge pyramid had gone ahead

A previous Top 10 list looked at buildings in London which perhaps shouldn't have been built. Today's is all about crazy building projects that never came to be.

The Top 10 of London by Alexander Ash, published by Hamlyn

The capital's skyline and some of our most recognisable sights would be dramatically different from today if any of these schemes had gone ahead.

Here are the top 10 of mad ideas that never became reality:

1. Royal Palace next to Downing Street: Designed by Inigo Jones for Charles I in 1638.

2. A symmetrical and piazza-filled Square Mile: Proposed by Sir Christopher Wren after the Great Fire, the plan centred on the Royal Exchange. Other plans included a grid style layout, with each of the 55 blocks being a separate parish with a church at its centre.

3. A triumphal bridge between Lambeth and Westminster: Heavily featuring Corinthian columns designed by Sir John Soane.

4. An arched span on Tower Bridge: Horace Jones' original design would not allow larger ships to pass beneath it.

5. A 91-metre (300ft) pyramid in Trafalgar Square: Proposed by Colonel Trench in 1815, it would have covered almost all of the square at a cost of £1 million.

6. A 300-metre (1,000ft) Crystal Palace Tower at Hyde Park: To save space it was proposed to turn the hall on its side.

7. Cleopatras Needle in Parliament Square: Favoured by John Dixon, the engineer who transported the obelisk from Egypt.

8. An elevated cable car railway: Proposed by John Pym before work had started on the London Underground, to be named the Metropolitan Super-Way. With the Thames cable car crossing now open, this is the one project on the list to actually come true in some form.

9. A viaduct railway along the middle of the Thames: To avoid paying compensation for demolition, the route was to run from London Bridge to Westminster with stations on each bridge.

10. The Eiffel Tower at Wembley Park: The project ran out of funds, reaching only 46 m (150 ft) before being demolished in 1907.

This list is featured in The Top 10 of London, a book by Alexander Ash, published by Hamlyn, 10 www.octopusbooks.co.uk

Are there any of these schemes that you wish had actually happened? Do you know of any other hare-brained building projects which nearly happened but didn't? Add your comments below.