Yoko Ono unveiled a monument in memory of her husband, Beatles member, John Lennon, in Iceland on Tuesday.
Ono lit up the Imagine Peace Tower on Videy island near the Icelandic capital Reykjavik's harbour on what would have been Lennon's 67th birthday.
The former Beatle was shot dead outside his New York apartment building on December 8, 1980 by Mark David Chapman.
Ono was joined at the ceremony by the couple's son, Sean Lennon, Beatles drummer Ringo Starr and bandmate George Harrison's widow Olivia.
"Image Peace Tower was visualised with love, and realised with love. It is a gift from John and Yoko and the people of Iceland, to the world,'' Ono said at the ceremony.
''Happy that the light tower is finally a reality after forty years," she added.
Paul McCartney also was invited, but did not attend.
The tower is a beam of light, radiating from a wishing well bearing the words "imagine peace" in 24 languages.
The plan is for it to be lit each year between his birthday, October 9, and the anniversary of his death on December 8.
Ono, an artist, said she had gathered hundreds of thousands of wishes for world peace at gallery shows around the world.
The wishes will be stored in capsules and buried on the island, each topped with a tree.
Ono, 74, has said she came up with the concept for the light tower in 1965 and that Lennon was interested.
She said the world was less peaceful now than 40 years ago, but she said her faith in humanity was not shaken.
She said she chose Iceland, the world's northernmost country, because it was a very eco-friendly country that relied on geothermal energy.
"The ground is very pure," Ono said.
"It's beautiful. With all that, I just had to do it in Iceland. It's a very magical country."