He spent 18 years behind its bars, and now a drawing sketched by Nelson Mandela of his former Robben Island prison cell is going up for auction.
The artwork, which shows the late South African president's cell door, a key sitting in its lock, will be sold by Bonhams next month.
The piece is one of a series of sketches Mandela created as part of a therapeutic activity in 2002, The Guardian reports, and was previously unseen by the public before going up for sale.
“For him, painting was a way of relaxing, but also making sense of the past,” said the politician's daughter Makaziwe, who is selling the drawing.
“This work held a particular significance for him as it was a constant reminder that he could not forget what seemed unforgettable and that he should not take freedom for granted.”
Mandela was incarcerated at Robben Island between 1964 and 1982, serving the rest of his 27-year sentence at two other jails in South Africa.
His cell at Robben Island, which measured just eight feet by seven feet, can now be seen by visitors to the inactive prison.
"Prison itself is a tremendous education in the need for patience and perseverance. It is above all a test of one's commitment," Mandela wrote of his time behind bars in his autobiography, Long Walk to Freedom.
The anti-apartheid activist's sketch will go under the hammer on May 2, The Guardian adds, in the first auctioned sale of Mandela's work in the US.
