The Sustainability Treehouse is part of the Gateway Village at the Summit Bechtel Scout Reserve in West Virginia. The main structure of the Treehouse is entirely architecturally exposed and was fabricated from weathering steel to withstand the exterior elements in the most sustainable way possible. The steel megaframe is approximately 150-ft tall and combines space-truss and moment-frame lateral systems. At its top, a large photovoltaic array soars above the surrounding tree canopy. Two enclosed box structures were prefabricated and mounted onto the main structure through four pedestal connections. The box structures consist of enclosed steel HSS welded trusses and frames with infill wood framing for walls and floors. Extensive 3D modeling and structural analysis was required to address the complex and irregular geometry of the Treehouse structure. Because the majority of the building consists of architecturally exposed structural steel, every connection was care-fully studied in 3D and detailed for optimal visual appearance. All wood members, both sawn lumber and glulam, are made of FSC southern pine. In an effort to tread lightly, we conducted extensive 3D modeling of the existing site conditions and different foundation systems to minimize the structure’s impact on existing ground flora and fauna. This effort included analysis of existing tree locations and the shielding of existing tree drip lines and root extents from the impacts of foundation and construction works.