High Quality Content by WIKIPEDIA articles! The X-Seed 4000 is the tallest building ever fully envisioned, meaning that the designs for construction have been completed. The X-Seed 4000 "is never meant to be built," says Georges Binder, managing director of Buildings & Data, a firm which compiles data banks on buildings worldwide. "The purpose of the plan was to earn some recognition for the firm, and it worked." Its proposed 4000m (2.485 miles) height, 6 km (3.728 miles) wide sea-base, and 800 floor capacity could accommodate five hundred thousand to one million inhabitants. It was designed for Tokyo, Japan by the Taisei Corporation in 1995 as a futuristic environment combining ultra-modern living and interaction with nature.