Object 825 GTS (K-825) - an Underground Submarine Base in Balaklava - a secret military facility during the Cold War situated in the Balaklava Bay.

Balaklava has been selected for the construction of the underground complex is not accidental. The very nature of the bay made the city an ideal hiding place for the navy. The narrow strait width of 200-400 meters covers not only the harbor from the storms but also from prying eyes. The large depth up to 17 meters allows submarines to enter the bay in submerged position. Mountain Tavros in which is located the secret object consists of a solid marble-like limestone. The thickness of the rock above the underground facilities reaches 126 meters.

Underground Submarines Base in Balaklava was built in 1957-1961. Object 825 GTS was conceived as the construction of anti-nuclear defense of the first category by Iosif Stalin who was impressed by the results of the bombing of Japan and looking for ways to protect the navy. The cost of the construction of Underground Submarines Base 825 GTS was 67 million Soviet rubles and the cost of equipment and life support systems - 65 million Soviet rubles.

Object 825 GTS is a combined underground water channel to the outputs on both sides of Balaklava mountains, the dry dock, repair shops, warehouses for storage of torpedoes and other weapons, housing for staff, dining room, kitchen, bathrooms, showers, rest rooms, command posts and nuclear shelter. It can accommodate seven major submarines of 613th and 633rd Soviet projects.

The submarines of Project 613 ("Whiskey" according to NATO classification) - a series of Soviet medium-sized diesel-electric submarine built in 1951-1957. Series has become the most massive in the Soviet submarine fleet - it was built 215 submarines.

Submarine Project 633 ("Romeo" according to NATO classification) - a series of diesel-electric submarine built in the Soviet Union in 1957 to 1961 - it was built just 20 submarines.

With the threat of nuclear attack three thousand workers can hide in Underground Submarine Base. The protection of the complex can withstand a direct hit by a nuclear ammunition capacity to 100 kilotons that is five times greater than the bomb dropped on Hiroshima.

Ability to completely isolate the object from the external environment provide autonomous air supply, powerful diesel generators, fuel and water lines, underground rail road.

After closing in 1993 most of the complex is not guarded. In 2000 the facility was transferred to the Naval Forces of the Armed Forces of Ukraine. In the period from 1993 to 2003 Underground Submarines Base was looted. Sevastopol "Marine Assembly" led by Vladimir Stefanovskiy proposed the project "Cold War Museum" in Object 825 GTS. So on 1st of June 2003 "Cold War Museum" as well as Underground Submarines Base Object 825 GTS was open to the public and tourists.