Beginning in 1965, Nevelson explored materials such as transparent industrial plastics and enameled metal. Her organization and forms became more geometric and systematic, resulting in more open and less densely packed sculptures. She sought clarity and transparency through both her materials and compositions. Her use of more durable materials for the large-scale walls led her in 1969 to accept her first commission for an outdoor sculpture. In 1971, she was inspired to combine found elements with deliberately fabricated pieces in freestanding constructed sculptures. Botanical imagery predominated in her new welded metal sculptures and their shapes, like their titles, suggest flowers, trees, gardens, and landscapes. MIT`s Transparent Horizon of 1975 is a part of this phase of Nevelson`s development. Its openness, horizontal disposition, and frontality recall her tabletop landscapes of the 1940s, grounded in the Surrealist sculpture of Alberto Giacometti. The piece is an amalgam of two earlier painted aluminum sculptures: Tropical Tree IV of 1972 and Black Flower Series IV of 1973. The revision and transformation of older works by melding them into new ones is typical of Nevelson`s sculptural practice. The shorter portion of Transparent Horizon, Tropical Tree, is composed of flat frond-like projections from a trunk-like core. The taller, Black Flower, shows vertical stems and spiky leaf-forms jutting out to the sides, capped by overlapping petal shapes. Her vocabulary of forms—imaginative abstractions from and transformations of nature—were influenced by Dada and Surrealist biomorphic abstraction, not only via Giacometti and David Smith but also Jean Arp`s painted wood reliefs of 1916-17. As the title of the final sculpture indicates, the piece gives the impression of plant-like verticals rising from a landscape while simultaneously suggesting elements of a gate or passage. Nevelson herself has stated that “it stands like this door, straight and frontal… you don`t see it standing isolated, you see it extending… the environment becomes its frame.” This frame is a constant image and organizing principle in her boxes, reliefs, and walls and is indebted to the sculpture of her friend David Smith, for whom the planar, frontal space-frame was a lifelong and constant theme. Nevelson considered herself “an architect of shadows” and maker of spectral shapes and primordial images. The forms in MIT`s sculpture suggest botanical processes of growth and decay. Transparent Horizon stands like a totem: somber, enigmatic, and magical.