As ceremonies take place around the world to remember victims of the 9/11 attacks, around 2,000 workers are building a huge development at Ground Zero in New York.

Six skyscrapers, a museum, two massive waterfalls where the twin towers once stood, a performance centre and a rail terminal are gradually taking shape nine years after the attacks.

Work at the 17-acre site has been delayed by disputes over whether the essence of the buildings should be commercial or commemorative. Finally there has been a compromise, with a mix of both retail, office and memorial space known as One World Trade Center.

Responsibility for the site is divided between the governors of the states of New York and New Jersey, who own the land through the Port Authority and Larry A Silverstein, the leaseholder who holds the right to redevelop the office space.

Tower 1 - The centrepiece, formerly known as Freedom Tower and now as One World Trade Center. Its planned height is 1,776ft (540m) echoing the date of the founding of the republic. It will be America's tallest building, housing offices, an observation deck, restaurants and broadcast facilities. The project architect is David Childs of Skidmore, Owings and Merrill. Estimated completion date is 2013.

Tower 2 - Also known as 200 Greenwich St. At 79 storeys high with a diamond shaped top and an 80-foot antenna, it will be the second-tallest skyscraper in NYC.

Tower 3 - Also known as 175 Greenwich St, it will be the third-tallest building on the site and include shops, offices, trading floors. It's scheduled for completion in 2014.

Tower 4 - The Port Authority of New York and New Jersey and the City of New York will take two-thirds of the office space at 150 Greenwich St. It is due for completion in 2013. Towers 3 and 4 were designed by architects Richard Rogers and Fumihiko Maki.

Tower 5 - 130 Liberty Street will stand on the site currently occupied by the remains of the Deutsche Bank building, which was badly damaged by the 9/11 attacks. New York University has expressed an interest in leasing the building.

Plans for a Tower 6 were abandoned.

Tower 7 - or 7 World Trade Center, opened in May 2006 and is two-thirds leased. It includes a park and central plaza with 30ft-wide fountain. Tenants include its owner Silverstein Properties and Moody's Corporation, WestLB, Ameriprise Financial, Dutch bank ABN AMRO, and Mansueto Ventures, publisher of Fast Company and Inc magazines.

The National September 11 Memorial & Museum comprises a museum, waterfalls and a park.

The museum is being constructed underground and will boast interactive displays explaining the 9/11 and 1993 terrorist attacks, as well as the part of the huge slurry wall that held back the Hudson River during the attacks.

At the twin towers there will be two massive waterfalls over illuminated pools. Names of the 9/11 victims and those of the February 1993 World trade Centre attacks will be inscribed around the edge of the memorial called Reflecting Absence and designed by architect Michael Arad and landscape architect Peter Walker.

The 1,000-seat performance arts centre to be designed by Frank Gehry will be home to the Joyce Theater which specialises in modern dance. Film festivals will also be held there.

The transportation hub will house a state-of-the-art rail terminal featuring retractable 150ft (46m) high "wings" made of glass and steel will let natural light to pass through to platforms 60ft (18m) below street level.