Standing nearly ten feet tall, Cubi XXI belongs to a series of twenty-eight large-scale, geometric, stainless steel sculptures that Smith made between 1961 and 1965. These compositions of prefabricated, welded geometric forms, widely considered to be among the artist’s greatest works, recall Smith’s earlier use of abstract figuration. Cubi XXI, for example, evokes a type of classical sculpture in which a human figure leans against a vertical support, such as a tree or a column. The Cubi works are also informed by the essential qualities of Cubist painting and are composed so that individual elements appear to shift when viewed in relation to each other. Additionally, their large, geometric shapes point toward the advent of Minimalism in the 1960s.