Gunkanjima - Hashima
Hashima Island, better known as Gunkanjima was undersea mine belonging to Mitsubishi since 1890. In 1959, the island's population reached its peak of 5,259, with a population density of 83,500 people/km2 -- a world record that remains until today. The island was emptied in 1974. Travel to Hashima was re-opened on April 22, 2009 after 35 years of closure.
This series pre-dates the limited opening of the island, when access required smuggling oneself on fishing vessels.