Sir Chris Hoy helped design the 6,000-seat velodrome
Construction has begun on the velodrome for the London Olympics, which organisers hope will be the fastest cycling track in the world by 2012.
The Olympic Delivery Authority (ODA) said the venue will give British cyclists and aspiring Olympians and Paralympians a place to practice.
Beijing Olympic gold medallist Sir Chris Hoy helped design the 6,000 seat venue in Stratford, east London.
The former West Ham tip site will cost £105m to transform.
The 2012 velodrome is being constructed by ISG and has been designed by Hopkins Architects.
Lord Coe, London 2012 chairman, said: "Britain leads the way in world cycling and deserves a world-class stage in 2012 so the start of work on time on a landmark new cycling venue for London is a significant milestone."
Olympics Minister Tessa Jowell said: "Today we've witnessed the start of construction of what, with the help of Sir Chris Hoy who helped design the velodrome, we hope will be the fastest track in the world for London 2012, helping Olympic and Paralympic cyclists better their awe-inspiring performances last summer."
The chairman of the ODA John Armitt said the velodrome would be a "world-class cycling venue with a record-breaking track for events in 2012 and the legacy of first-class facilities to help create the next generation of Olympic champions".