 Busch (p. 27) also places the sculptures of Jane Frank, as well as some works by Tony Smith and David Smith, in this category.Some environmental sculpture so encompasses the observer that it verges on architecture.George Segal, Duane Hanson, Edward Kienholz, Robert Smithson, Christo, and Michael Heizer are well known practitioners of the genre, although Segal and Hanson's work is figural.