Heathrow airport could be replaced by 190,000 new homes, a factory or swathes of parkland, according to plans revealed by architects.
London mayor Boris Johnson is especially keen on the plans to develop a "Heathrow City", given his backing for a new airport in the Thames estuary.
The designs were backed by Johnson and commissioned by Transport for London (TFL) and the mayor believes that the UK's scant supply of housing means new homes are sorely needed.
The new plans would only be implemented if the third-runway option is rejected and a new airport is built on the Thames.
Three visions were offered for the proposed redevelopment.
Architects Maccreanor Lavington envisage a "fully functioning city within the capital" and would plant woodland to add greenery to the vision.
Rick Mather Architects would transform the airport into a hub city, using runways and terminals as the skeletal structure for the new conurbation and connect 10 local centres. The hub would be predominantly for research, technology and manufacturing.
Hawkins Brown offered plans for a factory which would create jobs making self-build modular homes; houses that can be built to the purchaser's specifications.