An island known as Hashima, or Gunkanjima, located off the coast of Nagasaki, Japan, once held the world's highest population density. In the 1950s, residents lived in extremely close quarters, with some estimates suggesting that the island reached a density of 139,100 people per square kilometer in its residential areas. This record has never been matched. At its peak, the island was home to about 5,259 people. The island’s unique, battleship-like shape and towering concrete structures made it a striking sight, but its history is as complex as its appearance. Hashima's story began in the early 19th century when a coal deposit was discovered in 1810, transforming the previously uninhabited island into a key energy source during Japan’s industrialization. In 1890, the Mitsubishi Corporation began large-scale coal mining operations on the island, leading to a rapid increase in population. By 1950, the island was already home to 5,300 people, with a population density of 83,500 per square kilometer. To house the growing workforce, Mitsubishi built reinforced concrete structures, which gave the island its distinctive, almost futuristic look. During World War II, Hashima became a site of forced labor, with around 800 Korean and Chinese workers brought to the island. Tragically, 120 of them died under harsh working conditions. After the war, Japan shifted its energy focus from coal to oil, making the island’s coal mine obsolete. The mine was closed in 1974, and all residents left within a few months. Unlike many abandoned places, Hashima was not left due to natural disasters or economic hardship but because of a national shift in energy policy. Today, Hashima stands as a ghost island, with its buildings eroded by salt and wind, creating a post-apocalyptic atmosphere. The island has become a popular location for filmmakers, including a James Bond movie. However, its inclusion in the UNESCO World Heritage list has sparked controversy, particularly from South Korea, which views the island's history as a painful reminder of Japan’s use of forced labor during the war. Despite its eerie beauty, Hashima remains a symbol of both human ingenuity and the complex legacy of industrialization.