Russia: The Yamatau Mountain Underground Complex - A Visual History Oct 2026

A declassified CIA report from January 1984 provides a good analytical baseline (1). According to the report, the complex was in the initial stages of construction in January 1978 and had three parts: an operations area with several construction sites; a large housing/support area (now the city of Mezhgorye); and a construction support complex near the town of Tatly, 25 km to the SSE. A rail spur originating from the main rail line near the town of Tatly was under construction.

The intelligence report description aligns with the facility as seen on the earliest satellite image from circa 1985 (Graphic 2). All the construction sites could be identified, as was evidence of excavation. The rail spur to the housing/support area had been finished and a new power line extended to the operations area. A dam for a small lake was being built north of the complex.

Main Construction Sites

The complex could be seen in more detail in January 2008. Much of the heaviest excavation had probably taken place and some support buildings had already been removed. Most of construction centered around two sites with horizontal tunnel adits situated at the 800-meter-elevation-level. The rail spur now extended to the largest of the sites. (Graphic 1).

The first of the underground sites to be finished has a single entrance concealed by a 125-meter-long passageway. After a long period of inactivity, by May 2017 a 160 x 60-meter hardstand three probable helipads were constructed next to the entrance. The helipads were delineated only by dashed markings, suggesting an effort at deception. Security access to the entrance was improved 2018 and 2025, and the passageway received a new roof (Graphics 3 & 4). Vehicles were routinely present.

By 2008 the other construction site had a large number of buildings including a powerplant and a fire station; major features included a covered adit entrance served by two long accessways (one added after 1985), a large high-bay building (125 x 90-meters, newly-built, 1985), a group of vertical shaft buildings (not present 1985) and a railyard. By 2011 the large building had been dismantled, exposing a second adit entrance. The rail yard and the vertical shafts had probably been abandoned (Graphics 5 & 6).

Site clearing took place from June 2025 and August 2026 indicating major work had ended; the second adit was earth-covered, and the vertical shaft buildings were removed (Graphic 7). The clerestory roof of a building attached to one side of the adit access-way was removed, while activity increased at a materials handling area on the other. Three large warehouse-type buildings were built or improved and a concrete batch plant had been expanded.

By August 2026 the site was reconnected to the complex rail spur by a single track(; the rail yard remained abandoned Graphic 7). This development was part of a general reconstruction of the entire rail spur, which by at least 2022 was no longer in use. By August 2024 an approximately 20-kilometer segment of the spur had been rebuilt, with ongoing work seven kilometers from Mezhgorye (Graphic 8). As at the construction site, the newly-laid rail was confined to a single track; multiple-track railyards in the city and south support areas remained abandoned.

Other Construction Sites

The three sites with vertical shaft buildings were above and below the main construction sites and their locations suggest some tunneling took place in the direction of the city (Graphic 9). The highest of these (1000-meter-level), and the one with evidence of most excavation, appeared to have a venting system. The next vertical shaft (600-meter-level) is directly below the main construction sites and also showed signs of excavation. Very little evidence of activity was ever seen at the third shaft site located only 900 meters from the edge of the city and near the barracks.

The possible underground construction site is immediately northwest of Mezhgorye (Graphic 10). The site was visible in 1985, but was inactive after 2008 by when support buildings had been removed. However, in 2014 a circular, 12-meter area was exposed during continued clearing. Work around the area continued between 2017 to 2021, culminating in the construction of a high-bay building over the site.

Mezhgorye City & Other Infrastructure

A closed city, Mezhgorye can only be reached through a control point three kilometers to the south. Access to the mountain sites is controlled by another security point at the 700-meter-level (Graphic 11). The city was already well established in 1985 and largely attained its present size by 2008. Prominent facilities include two support areas, a barracks with a large vehicle park and a powerplant (Graphic 12).

There are few communications facilities. Possible cell towers can be seen near a communications building and the fire station. A larger tower was installed in the vicinity of the hospital in 2017 and a similar one was installed at Tatly about the same time. Three helipads in the vicinity of the barracks since at least 2008. The pads were snow-cleared and useable through 2022, but by 2025 appeared to have been abandoned.

Reference:
(1) CIA-RDP84T00171R000301360001-9; Yamatau Mountain Underground Construction Project, USSR, 10 January 1984