Traffic will be banned from several central London roads for an event which aims to persuade more people to cycle around the capital.
Blue Peter presenter Konnie Huq (left) will take part in the event
London Freewheel will encourage thousands to cycle a 14km (8.7 mile) traffic-free route on 23 September.
Mayor Ken Livingstone said: "I hope people will find that cycling regularly in London is easier than they thought."
It is estimated that 40% of Londoners have access to a bike but only 5% use one regularly.
The route will pass several London landmarks including the London Eye, Victoria Embankment, Westminster, St Paul's Cathedral and the Mall.
Riders will be led onto the route by experienced cyclists from six "hubs" across the capital. Participants will also be able to have their bikes checked by experts.
The Sunday event will culminate in a festival at St James's Park for riders, including bike stunt displays, a cycling circus and information on cycling in London.
The number of cyclists on London's major roads is estimated to have grown by about 80% over the past seven years, but Transport for London wants to increase it further.
Blue Peter presenter Konnie Huq was the first person to sign up for the free event.
She said: "Cycling is fun, gets you fit and is a great way to travel around London. I hope this event encourages more people to take to two wheels."
Meanwhile two lorries have been parked in Trafalgar Square, central London, for a road safety event on Tuesday and Wednesday.
The aim is to highlight the dangers posed by lorries to cyclists and pedestrians by demonstrating how limited a lorry driver's vision is.
Metropolitan Police figures show that nine cyclists were killed in London in 2006 in accidents involving lorries.