Tim Halbur

In the U.K., new carbon emission standards may mean that great numbers of buildings from the 1960s and 70s will need to be demolished.

A group of investors bought New York City's Stuyvesant Town and Peter Cooper Village in 2006 at the height of the market for $5.4 billion. The speculative deal is now underwater and the investors have decided to walk away from their loans.

'I'm pretty convinced we're in the midst of a transformation which is probably as profound as what happened immediately after the Second World War,' says planner Ken Greenberg in an interview in Metropolis.

Raymond Joseph, Haitian ambassador to the U.S., sees the opportunity to build a smaller, better city from the ruins.

While cities may seem permanent, a group called Architecture 2030 claims that a majority of the buildings in cities today will be rebuilt by the year 2035.