Ancient Alien Theory~ many ancient cultures believe their ancestors were visited by "star brothers" who came from the sky. This is one example of, what some believe, is a depiction of ancient advanced technology: Stele D, Mayan site of Quiriguá, Guatemala
Abandoned Battleship Island, Japan housed what it should have with obscenely crowded apartments like this. Now, entire island is abandoned & restricted to the public. These derelict sky-scraping ghettos fall without an ear to hear them.