As referenced in the post, “The Top 10 Buildings in Tokyo“, Shinjuku’s skyscraper district used to be occupied by the Yodobashi Water Purification Plant 淀橋浄水場. Seen here is a map from circa 1945; Shinjuku Station occupies the center of the map, with the water purification plant located to the left (west). To the right (east) is Shinjuku Gyoen National Garden.
For comparative photos of the purification plant then and now, see: Tokyo then-and-now: an anthology