A £1m permanent memorial to the victims of the 7 July 2005 London bombings is to be unveiled in the city's Hyde Park.
Fifty-two people were killed and hundreds more injured when suicide bombers detonated backpacks on board three Underground trains and a bus. Families of those killed will gather later to see it publicly revealed.
Relatives who have seen the 52, 3.5m (11.5ft) tall stainless steel pillars - grouped to represent the attack sites - say they form a "fitting tribute".
Architects Carmody Groarke wanted to convey the random nature of the loss of life - how it could have been anyone travelling in London that day. Director Kevin Carmody said the firm worked closely with the families through monthly liaison meetings to ensure the finished product was what they required.
"It took a long time to get to the strong ideas like symbolising the single and collective loss of life," he said.
He said 26 of the columns - known as stelae - were grouped to represent those killed on the Underground near King's Cross.
Other clusters represented Tube bombing victims at Aldgate and Edgware Road, with the remainder symbolic of those who died on the number 30 bus in Tavistock Square.
"Hopefully people will have an almost magnetic propulsion towards it," said Mr Carmody.
He said it could be viewed from afar as a single entity but that as they moved closer, people would discover the significance of the four groupings and individual columns. Though the stelae are anonymous, they are inscribed with the date, time and location of the bombings they represent.
"We're very happy that the families are pleased with the result," Mr Carmody added.
A representative of the bereaved families' group said: "The memorial is a fitting tribute, honouring the 52 lives lost on 7 July 2005, ensuring that the world will never forget them.
"It represents the enormity of our loss, both on a personal and public level.
"We hope this memorial will speak to visitors so they can understand the impact of these horrific events."
It is located between the park's Lover's Walk and Park Lane.
Thanks to the open casting process used to make the columns, with molten stainless-steel being poured into sand moulds, each one has a unique finish.
Saba Mozakka, 28, from Finchley, north London, was one of six family members to sit on a liaison board during the memorial's design. Her mother, Behnaz Mozakka, 47, a biomedical officer, was killed on a Piccadilly line train near King's Cross station while commuting to work. Ms Mozakka described the memorial as "truly incredible".
"I'm very happy. It's very poignant," she said.
"It's an amazing tribute to my mum and the 51 others who were so viciously and brutally taken from us."
Prince Charles and the Minister for London, Tessa Jowell, will address the unveiling ceremony on Tuesday, before the names of the victims are read out and a minute's silence is observed.
The prince will then lay a wreath on behalf of the nation while the Duchess of Cornwall will leave a floral tribute for the families.
Prime Minister Gordon Brown, Conservative leader David Cameron, Liberal Democrat leader Nick Clegg, London Mayor Boris Johnson, former mayor Ken Livingstone and senior figures from the emergency services will also attend the event.