Tomohiro Hata Architect and Associates designed House in Koyoen for a site in Koyoen, Japan, where retaining walls and winding roads define the neighborhood. The area developed over time through successive construction, leaving walls of varying ages that shape how residents move through the terrain.

The house uses wooden arches arranged back to back in cross-shaped columns. These repeated structural elements create an open frame that responds to the site's multiple levels and directions. The small wooden members assemble into a larger system that connects to the surrounding slopes and pathways rather than standing separate from them.

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The structure's multi-directional framework extends space beyond the building's footprint. By aligning with the roads and retaining walls, the house integrates with Koyoen's layered topography instead of imposing a single orientation onto the sloped site.