Located in a park full of trees by the Grand Canal River on the east side of Beijing, the project started without a clearly defined program. The project is the space to be flexible for different functions (library, bars, event space, gallery, office, etc.). Inspired by No-stop city, a utopian urban design proposed by Archizoom in 1960s based on indeterminism, Forest Building explores a spatial system generated from additive units responding to the uncertainty of program, as well as structural form and construction system responding to the character of the site.The design for this prototype was inspired both by the ancient Chinese wooden building system, in which structures can be taken apart and rebuilt elsewhere with little damage, and by Le Corbusier’s Pavilion for Zurich, which summarized his lifelong research on modular building systems. It comprises a series of hexagonal cells with architectural, structural, and mechanical systems all synthesized within the same geometrical rules. The composition of the cells can be rearranged according to different site and programmatic needs.