Hotel D is a distinctive residential facility completed in 1977, located in Sugadaira, Sanada Town, Shimoina District, Nagano Prefecture. Designed by renowned architect Toyo Ito, this building exemplifies the modernist approach that characterizes his early work. Situated in the mountainous terrain of Nagano, Hotel D showcases Ito's innovative design philosophy and his ability to harmonize architecture with its natural surroundings. The structure reflects the architectural trends of the 1970s while maintaining functional excellence as a hospitality establishment, making it a significant example of contemporary Japanese architecture from that era.