Work has begun on the £3.5bn project to build the replacement to the World Trade Centre in New York.
Bulldozers moved into the pit on the site to begin building the 540 m Freedom Tower, as well as three other high rises and a residential tower.
These buildings will surround a memorial, museum and cultural centre dedicated to what relatives of those who died in the 11 September attack consider to be a sacred site.
Construction is expected to complete by 2011 or 2012.
Work began a day after developer Larry Silverstein and the land owner, the Port Authority of New York and New Jersey, resolved long-running and acrimonious disputes over money, security and design.
Silverstein said: "What is so spectacular is the opportunity to come together as we have in the last few days for the purpose of rebuilding the World Trade Centre. It's of great significance to me and to all New Yorkers."
New York governor George Pataki said: "We are not going to build low in the face of a war against terror. We are going to soar to new heights and reclaim New York's skyline."
Pataki symbolically laid the first stone on 4 July, 2004, just ahead of that year's Republican National Convention, which was held in New York.