Building work has started on the last Olympic Park venue in east London, the Olympic Delivery Authority (ODA) said.
The Eton Manor site will be the aquatics training centre for the Games.
The site will also be a key venue for the Paralympic Games and will host the wheelchair tennis event, catering for up to 10,500 spectators.
The facility will be revamped after the Games to include two hockey pitches, six tennis courts, and provision for five-a-side football pitches.
John Armitt, chairman of the ODA, said: "During the Olympic Games, Eton Manor will be an aquatics training venue, housing three Olympic-size temporary swimming pools, a temporary synchronised swimming pool and a temporary water polo pool.
"During the Paralympic Games, it will host the wheelchair tennis competitions with temporary seating for 10,500 spectators."
Seb Coe, chairman of the London 2012 Organising Committee, said: "It will also leave the legacy of a multi-purpose sports centre for community usage afterwards.
"It is the first time in the history of Paralympic tennis that a centre has been purpose built for the wheelchair tennis event."