Four months of secrecy surrounding the submissions and their designers ended as the works went on display in New York's Winter Garden. Each design seeks to find an architectural response to the emotional trauma of the attacks. On February 26 1993 six people died when a bomb exploded at the World Trade Centre and almost 3,000 people died in the al-Qaida attacks on September 11 2001.
The winning memorial, to be chosen by the end of the year, will accompany Daniel Libeskind's jagged towers, which were chosen in February to replace the World Trade Centre itself.
"We have sought designs that represent the heights of imagination while incorporating aesthetic grace and spiritual strength," the jury that chose the finalists said in a statement.
The shortlist was selected from 5,200 entries by a 13-member jury including representatives from the police, fire department, victims' families and the Lower Manhattan Development Corporation which is overseeing the rebuilding of the area. All the designs preserve the huge wall of the trade centre's basement, the only surviving remnant of the original complex.
"I thought they captured the essence of what the memorial should be," said Christine Huhn-Graifman, whose husband died in the 2001 attack. The families, who were shown a preview of the designs on Tuesday night, described the designs as "reverential" and "respectful", but some were disappointed that more use was not made of the twin towers' foundations.
Artists were asked to submit work which met four criteria: to remember and honour the families, respect a place made sacred by the loss, recognise the endurance of those who survived and reaffirm the respect for life.
"Their designs draw upon the elements of light, water, earth and life itself," said John Whitehead, chairman of the LMDC.
Reflecting Absence, by Michael Arad, proposes two pools submerged 30 feet below street level in the middle of a "field of open cobbles" on an open piazza. Individuals' names would be engraved on a stone parapet surrounding the pools while a candle-lit passageway would be created for victims' families.
Dual Memory, by Brian Strawn and Karla Sierralta, comprises two works. An "individual memory footprint" where the north tower once stood is described as a "floating plane of water over an enclosed pavilion" which will project images, stories and the victims' names.
At the site of the south tower, the artists have proposed a "shared memory footprint" with 92 sugar maples using soil from 92 countries and messages of hope carved on stone walls.
Following the very public disagreements that emerged between property developers and architects over the main building, selection of the memorial has been conducted under tight supervision. Entrants were warned that they would be disqualified if they disparaged the LMDC, jurors or other designs, or revealed the authorship of any design concepts to jurors or reporters.
"The reasoning is to ensure this becomes a dialogue of ideas and not personalities and that a public relations campaign doesn't erupt," Matthew Higgins, of the LMDC, told the New York Times.
