Matua Island is located near Kuril Islands group's center - an archipelago in Sea of Okhotsk (northwest Pacific Ocean). Several scientific expeditions made significant archaeological findings on the island, the biggest of which were the remains of a Japanese long-range warplane from WW2 (1939-1945). Among the other discoveries were various Japanese weapons, army boots, kitchenware.
Matua was first mentioned in the early 18th century as home to an Ainu settlement. Eventually Japan took the island and by the beginning of WW2 transformed it into a fortress with navy docks, an airfield (east-west oriented, length 1330 m / 4360 ft), underground canals and an extensive network of communications.
In 1944, US navy aircraft bombed the island facilities, while US warships shelled it. During the attacks, several Japanese cargo ships were sunk near the island or while docked at the harbor. In August 1945 (last weeks of WW2) during the Battle of the Kuril Islands, the Japanese garrison (7000-8000 men) on the isle surrendered (without firing a single shot) to the Red Army troops. Soon, the USSR (Soviet Union) established on the island a border patrol outpost. Since 2001, when the military personnel left the station, the isle became uninhabited.
In 2003 was organized an expedition from the Kamchatka Peninsula (Russia) to Matua island. In the following years were mounted 15 more expeditions. What the Russian expeditions found on the island were numerous trenches and man-made caverns. The isle's northern part is naturally protected by a 1496 m / 4910 ft high volcano (Sarychev Peak) with a steep-walled crater. The rest of the territory was transformed into a stronghold, ringed by pillboxes (concrete dug-in guard posts), some of which are carved into the rock.
According to legends, there is an underground city on the island, that during WW2 housed biological warfare and nuclear research laboratories.
In June 2016, around 200 Russian technical experts made an expedition to Matua (watch the YouTube video - in Russian). A future plan includes rebuilding the airfield and establishing a Russian military base on the island.