Spectra is the name of a series of art installations by Ryoji Ikeda which use intense white light as a sculptural material. The most recent presentation of spectra was in Hobart, Tasmania, Australia for four days ending 24 June, 2018 to mark the winter solstice, and as an installation piece at the Dark Mofo festival held by MONA. spectra [Amsterdam] was the first presentation of the work in 2008 its current form; an array of xenon lamps pointed skywards lit from dusk till dawn accompanied by a mathematically derived score audible from each of the lamp bases. The work was first commissioned and produced by Forma Arts.

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".