Wish Tree for Bilbao is a participatory work created by the artist as part of a series she began in 1996, inspired by the Japanese tradition of hanging prayers from a shrub, tree, or bamboo plant. In this work, the artist invites visitors to write down their wishes for peace, which, after being hung on the tree, are sent to Ono to be included in her project Imagine Peace Tower (2007). Created by Ono in memory of her late husband John Lennon (1940–1980), Imagine Peace Tower is an environmental light installation located in an open landscape on Viðey Island, Reykjavík, Iceland. Designed as a wishing well, it is symbolic of Lennon’s advocacy and Ono’s continuing campaign for world peace. The installation at the Guggenheim Museum Bilbao alternates between periods when visitors can write down their wishes and when they can whisper them to the tree. Ono has created different versions of this piece, which can be found in various museums, including the Peggy Guggenheim Collection in Venice, Museum of Contemporary Art Tokyo, Hirshhorn Museum and Sculpture Garden in Washington, D.C., and now the Guggenheim Museum Bilbao.