The Tokyo Tower of Babel would become the tallest man-made structure ever built, with a height of 10 km (6.2 mi).
Tokyo is the most populated of Japan's 47 prefectures. With around 14 million inhabitants in the prefecture and 40 million in the Metropolitan area as of 2024,[1][2] Tokyo ranks among the largest metropolises in the world. Despite Japan being the country with the highest average age globally in 2024 (excluding the city-state of Monaco and Saint Pierre and Miquelon), according to The World Factbook,[3] and experiencing negative population growth,[4] the country underwent a period of rapid population growth after World War II,[5] particularly in the capital, Tokyo. This growth gave rise to several megaprojects aimed at addressing ecological issues and space shortages caused by overpopulation.[6] This article lists visionary megaprojects announced during the 1980s and 1990s, coinciding with Japan's asset price bubble period, as well as more recent projects with heights of 300 meters or more.
