4. Hashima Island, Japan

Nicknamed ‘Battleship Island’ for its unique silhouette, Hashima was once a thriving coal mining hub and among the most densely populated places on earth. As petroleum replaced coal in the 1970s, the island’s population vanished almost overnight, and Hashima was officially abandoned in 1974. Now, its stark concrete skeletons draw urban explorers and have served as inspiration for movies, offering a powerful visual of rapid industrial rise and fall.