Wish Tree is an ongoing art installation series by Japanese artist Yoko Ono, started in 1996, in which a tree native to a site is planted under her direction. Viewers are usually invited to tie a written wish to the tree except during the winter months when a tree can be more vulnerable. Locations of the piece have included New York City, St. Louis, Wish Tree for Washington, DC, San Francisco, Pasadena, and Palo Alto, California, Tokyo, Venice, Paris, Dublin, London, Exeter, England, Finland and Buenos Aires, Argentina, Calgary.

The Imagine Peace Tower is a memorial to John Lennon from his widow, Yoko Ono, located on Viðey Island in Kollafjörður Bay near Reykjavík, Iceland. Installed in 2007, it consists of a tall tower of light, projected from a white stone monument that has the words "Imagine Peace" carved into it in 24 languages. These words, and the name of the tower, are a reference to Lennon's campaign for peace, and his 1971 song "Imagine".