Object 825 GTS – The Submarine Base Under a Mountain

Object 825 GTS, a Cold War relic nestled in the Tavros mountain, was a formidable underground complex designed to house and maintain Soviet submarines.

Constructed from 1953 to 1961, this once-secret facility, capable of withstanding a nuclear explosion, has now been transformed into a museum,



The Unique Location of Object 825 GTS

Design Specifications

Object 825 GTS After the Cold War


To understand the significance of Object 825 GTS, it’s crucial to consider the broader context of the Cold War. This period, which lasted from the end of World War II in 1945 until the dissolution of the Soviet Union in 1991, was marked by a state of political and military tension between the Western bloc (led by the United States and NATO allies) and the Eastern bloc (led by the Soviet Union and its Warsaw Pact allies). This era was characterized not by direct military confrontations between the superpowers but by proxy wars, nuclear arms race, espionage, and ideological conflicts.

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The Soviet Union, keenly aware of its strategic position, sought to enhance its defensive and offensive capabilities during the Cold War. The development of nuclear weapons and the advancement of naval technology were key components of this strategy. The Black Sea, connecting to the Mediterranean, was of particular strategic importance. It served as a critical point for the Soviet Navy, offering a route for naval forces to project power into the Mediterranean and beyond.

Balaklava, a small town in Crimea, was chosen for its natural geography, which offered excellent protection and concealment. The surrounding mountains provided a natural shield, making the base less vulnerable to aerial reconnaissance and attack. This choice of location was also motivated by the need for secrecy, a hallmark of military projects during the Cold War. The Soviet leadership wanted a facility that could operate undetected, ensuring the security and readiness of its submarine fleet.

The entrance into the Balaklava Naval Museum, previously known as Object 825 GTS. Image by Alexxx1979 CC BY-SA 3.0

The construction of Object 825 GTS was shrouded in secrecy. Its very existence was unknown to the outside world, and even within the Soviet Union, only a select few were aware of its purpose and capabilities. This secrecy was maintained to prevent Western intelligence from gaining any knowledge about the Soviet Union’s submarine operations and nuclear capabilities. The workers and military personnel involved in the project were bound by strict confidentiality, and the town of Balaklava itself became a closed area.

During the Cold War, the threat of nuclear confrontation was a constant concern. Submarines, particularly nuclear-armed ones, played a critical role in the strategy of deterrence. Object 825 GTS was not just a facility for maintaining and repairing submarines; it was part of a larger network of military installations that formed the backbone of the Soviet Union’s defense and strategic deterrence posture. The base allowed the Soviet Navy to maintain a continuous presence in the Black Sea and beyond, contributing to the delicate balance of power during the Cold War.

The Unique Location of Object 825 GTS

Object 825 GTS was constructed in the heart of the Tavros mountain. It was designed to withstand a category-I nuclear explosion, equivalent to a yield of 100 kilotons.

At the core of this complex is an intricate underground network. It comprises water channels that serve multiple purposes, including a dry dock for submarine maintenance, repair shops equipped to handle a range of technical needs, and extensive warehouses. These warehouses are specially designed for storing torpedoes and a variety of other weapons.

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But the functionality of this complex extends beyond military logistics. One of its most crucial features is the capability to protect personnel from the catastrophic aftermath of a nuclear explosion – the dreaded nuclear fallout. This aspect highlights the strategic importance of the facility, not just as a military base but also as a shelter in the direst of circumstances.

A closer shot of the tunnel entrance. Image by Russianname CC BY 3.0

Strategically located within Tavros mountain, the complex boasts exits on both sides, ensuring quick access and a strategic advantage in terms of mobility and deployment. In times of dire need, caisson gates, an integral part of the complex’s design, can be deployed to seal off the entire structure, transforming it into an impregnable fortress.

The northern side of the mountain holds another strategic asset – an exit that leads directly to the open sea. This feature is crucial for discreet naval operations, allowing submarines and other naval assets to access the sea without detection.

One of the most striking aspects of this complex is its camouflage capabilities. The entrances and exits, carved into the mountain, are skillfully concealed with camouflage devices and networks. This not only adds to the element of surprise but also significantly enhances the facility’s defensive capabilities.

Design Specifications

This facility, emerging from the shadows of the Cold War, was designed for a specific purpose: to house, repair, and maintain Project 613 and 633 submarines, known in naval parlance as Whiskey and Romeo-class, respectively.

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Central to the design of Object 825 GTS is its imposing water channel, stretching an impressive 602 metres (1,975 ft) in length. This channel is not just a feat of engineering but also a strategic asset, capable of accommodating up to seven submarines simultaneously. But the facility’s capacity doesn’t end there; its various water channels, intricately designed, can house up to 14 submarines of different classes.

The channels’ dimensions are equally remarkable, with depths plunging to 8 metres (26 ft) and widths varying from a substantial 12 to 22 metres (39 to 72 ft). This expansive design underscores the facility’s role as a major submarine hub, covering a total area of approximately 9,600 square metres (103,000 sq ft).

Some of the immensely thick doors that allowed the site to withstand a nuclear blast. Image by Tostan CC BY-SA 3.0

During peacetime, the complex followed a rigorous protocol for equipment loading, primarily conducted on the pier. This process was executed under the vigilant eyes of the base’s personnel, who meticulously monitored the movements of spy satellites from potential military adversaries. In contrast, wartime operations necessitated a shift in tactics, employing a specially designed tunnel within the complex for discreet equipment loading.

A noteworthy addition to the complex is Object 280, a repair and technical base dedicated to the storage and maintenance of a nuclear arsenal.

A defining feature of Object 825 GTS is its underwater access point, enabling submarines to enter and exit the base in complete submersion. This feature not only provided a tactical advantage but also enhanced the secrecy and security of submarine operations.

Attention to detail is evident in the maintenance of the base’s internal environment. The temperature is consistently regulated at around 15 °C (59 °F), creating optimal conditions for both the machinery and the personnel stationed within.

The building of the subterranean complex spanned eight years, beginning in 1953 and concluding in 1961. During this period, approximately 120 thousand tons of rock were excavated from Tavros mountain. To maintain the utmost secrecy, supplies were delivered under the cover of darkness, transported by barge in the open sea.

Object 825 GTS After the Cold War

With the dissolution of the Soviet Union in 1991, the strategic landscape of the world underwent a seismic shift. Object 825 GTS, once a bastion of naval might and secrecy, found its role as a submarine base and nuclear arsenal storehouse redundant in this new era. The facility, which for decades had operated under the shroud of utmost secrecy, began a journey of transformation into a public museum.

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The decommissioning process involved the demilitarization of the base, removing sensitive equipment and ensuring that the facility posed no security threat. This process marked the end of an era for Object 825 GTS. The base was left ungaurded from 1993 until 2003 and subsequently looted, with vast amounts of the metal being taken for scrap.

However, its rebirth as a museum breathed new life into the facility. The very tunnels and docks that once echoed with the sounds of military activity were now silent, serving as corridors for visitors exploring the Cold War’s naval history.

The Soviet Navy also used the site to train Dolphins to attach explosives and beacons to naval assets. Image by Stanisław Ludwiński CC BY-SA 3.0

As a museum, Object 825 GTS serves a dual purpose. Firstly, it acts as a preserver of history, offering an unfiltered glimpse into the life and operations of a top-secret military facility during the Cold War. Secondly, it serves an educational role, informing visitors about the complexities of the era, the technological advancements in submarine warfare, and the delicate balance of power that defined the latter half of the 20th century.

The transformation of Object 825 GTS is symbolic of the broader changes in the post-Cold War world. From a facility designed to survive a nuclear apocalypse, it has become a site where people can learn about a past that is both intriguing and sobering. This shift from operational secrecy to transparent education reflects a move towards a more open, informed society.