The redevelopment of the World Trade Center site in New York has been a long process, but it is now gradually taking shape.
The architect Daniel Libeskind was tasked with creating the first design studies for the site. This led to the creation of his 'masterplan' for the whole area - which remains the foundation of what is taking shape.
Other architects have been commissioned by the developers Silverstein Properties, to work on the individual buildings. They include British stars Richard Rogers and Norman Foster.
Illustrated by architects' animations for how the finished site will look, Daniel Libeskind and Dara McQuillan, spokesman from Silverstein Properties, explain the thinking behind the development to the BBC's Ramon Goni.