Since the sixties, the works of the American artist Keith Sonnier have focused on artificial light, evoking a variety of associations with the aesthetics of advertisement and everyday life. The authors of the book at hand explore Sonnier's oeuvre, showing the artist´s innovative way of blending light and architecture by means of two of his recent light installations. In cooperation with the Austrian-born architects Baumschlager & Eberle, Sonnier designed a light installation for a subterranean passage of the Münchner Rück insurance company. Neon light in rich, deep colors fills the space, with the spatial qualities of light becoming perceptible in a highly sensual way. The installation for the parish church in Steyr-Resthof in Upper Austria, a new church building by the architects Riepl & Riepl, also inhabits a singular position in Sonnier's oeuvre to date. Sonnier's comprehensive concept turns the liturgical space into a light symbol, in the truest sense of the word elevating the "aura" of the building.