Stars mark two years to Olympics
Olympic champ Chris Hoy will be among the top athletes taking part in a special event to mark exactly two years to the London 2012 Olympic Games.
The cycling star will be joined by schoolkids as he rides the first lap in the new velodrome in east London.
American Michael Johnson will sprint on a special track inside the Olympic Stadium and Britain's John Amaechi will shoot hoops in the basketball arena.
Tickets for the sporting event will be available in spring next year.
Chris Hoy won three gold medals at the last Olympics in Beijing, China
Hoy said the next two years would pass quickly: "The Olympics are always there at the back of your mind. It's the main reason why you train every day."
The officials are using Tuesday's event to show off the progress made on building the Olympic venues.
There's also going to be a day-long event in London's Trafalgar Square, with lots of interactive games for the public.