Within the context of Conceptual Art, Sol LeWitt established systems of logic in the form of written instructions that governed the outcome of an artwork in advance of its execution. Traditionally, the worked surface of a drawing has been understood as the most intimate and direct record of an artist's creative process. With his wall drawings, LeWitt ensured that his autographic touch was wholly absent by leaving the execution to others. Despite their basis in impersonal written instructions, the mural surfaces of LeWitt's wall drawings nevertheless have the capacity to become quite visually sumptuous. Theatricality and decorativeness are evident in Wall Drawing #831 (Geometric Forms), a site-specific work and one of the first created in acrylic paint that LeWitt conceived for Gallery 208 of the Guggenheim Museum Bilbao in 1997, the year of the Museum's opening. Among the earliest of the artist's wall drawings in acrylic paint, this work is rendered in highly saturated, vibrant tonalities of red, blue, orange, green, purple, and gray. The irregular and cropped geometric forms bend with the curved and sloping walls of the gallery, so that the painting both merges with and transforms its architectural setting.