It has been 20 years since the 9/11 terror attacks shocked the world.
Four planes hijacked by 19 terrorists from Al Qaeda were flown at targets including the World Trade Centre in New York and Pentagon in Washington D.C. on September 11, 2001.
The 110 storey towers collapsed within one hour 42 minutes of being struck, while the west side of the US defence department headquarters was damaged.
A fourth plane, now believed to have been heading for the White House or Capitol Building, crashed into a field in Pennsylvania.
In total, 2,996 people died and more than 6,000 were injured as a result of the attacks.
One of the first memorials to appear was an installation of searchlights positioned at the footprint of the World Trade Centre towers.
In 2015, a monumental sculpture made from a section of the Twin Towers salvaged from Ground Zero was unveiled at Queen Elizabeth Olympic Park.
The 28ft-tall artwork with a mirrored finish - entitled Since 9/11 - was gifted to the UK by the Port Authority of New York and New Jersey in 2010.
This was on the condition it was sited in a prominent London location.
Visual artist Miya Ando wanted to create something that drew the eyes upward in the hopes of paying respect to those who were lost. Credit: Roy Ritchie
Nestled among silver birches on top of a mound outside Zaha Hadid's London Aquatics Centre, the four-ton piece is by the New York-based sculptor Miya Ando.
The American visual artist of Russian and Japanese heritage was approached by educational charity The 9/11 Project in 2009 to create a memorial to those lost in the attacks.
"It was a great honour and privilege to create a sculpture from hallowed material and a very, very heartbreaking several years as I worked on the sculpture," Ms Ando told the Recorder.
"I wanted to create something that redirected light and drew the eyes upward in the hopes of paying respect to those who were lost.
"I wanted to pay homage to the victims and families and create something respectful. It was a very difficult project, emotionally," she added.
Ms Ando, whose sister and friends were near the World Trade Centre at the time of the attacks, described the work as a difficult object to look at because its shape was determined by an extremely violent act.
"The steel is massive and extraordinarily thick and strong and yet it is bent and mangled. I hope this may remind people of the destructiveness of hate and violence and encourage peaceful thought and solutions to our differences," she said.
And she expressed the hope that, with it standing upright again, a piece of the building which had fallen could be a metaphor for the strength and resilience of the human spirit.
"My deepest wish, however, is that the piece properly respects the memory of those who were lost and to all of the many who suffer still to this day after 9/11," Ms Ando said.
In total, 2,000 pieces of steel were recovered from the Twin Towers and stored in Hangar 17 at JFK airport in New York between 2002 and 2010, when they were released to towns and cities across the US and overseas in time for the 10th anniversary of 9/11 in 2011.
London is the only European capital to receive this honour, according to The 9/11 Project.
The artwork won public support from figures including then-mayor of London Boris Johnson, the historian Simon Schama and Lord George Carey, a former Archbishop of Canterbury.
They backed a campaign to secure a permanent home for the artwork, which had been exhibited for four weeks in Battersea Park in 2011.
Mr Johnson unveiled the sculpture at Queen Elizabeth Olympic Park in the presence of then-US ambassador to the UK Matthew Barzun in March 2015.
"This pertinent reminder of the 9/11 atrocities is a tremendous addition to the park that encapsulated the spirit of hope and tolerance during our Olympic Games.
"Nearly 14 years may have passed, but this prodigious artwork will generate continued interest, discussion and memories in the thousands of visitors to its landmark new home," Mr Johnson said at the time.
You can get to the artwork either from the London Aquatics Centre or via Carpenters Road. It is free to visit and wheelchair accessible.
