Yubileyna

Yubileyna Cave (Jubilee Cave) is one of the remarkable and highly intriguing underground sites in Bulgaria, located within the karst-rich territory of the Peshtera municipality. Discovered in the mid-1970s, it features a complex two-story cave system that seamlessly combines dry chambers, narrow rock fissures, and active water-bearing galleries. The cave was developed and adapted for exploration thanks to the dedicated work of F. Filchev, turning it into a valuable site for both speleology enthusiasts and the Bulgarian scientific community.

Morphology, Layout, and Water Galleries

• Entrance and Initial Stage: The subterranean route begins at an entrance with a convenient diameter of about 2 meters. The entry corridor leads visitors into an opening that is heavily packed with massive fallen rock blocks.
• The Main Chamber: Right past the rockfall area lies the largest continuous space inside Yubileyna. This impressive hall boasts a length of 40 to 50 meters and a width reaching up to 17-18 meters.
• Main Corridor and Siphon: The primary gallery starts with a width of 4-5 meters, but over the next 40-50 meters, it narrows progressively down to a tight squeeze of just 0.5 to 1 meter. Past this bottleneck, the passage expands once more, opening directly into the active water gallery. The stream flows for about one hundred meters before terminating at a submerged siphon, beyond which the water reappears into the deeper, unexplored recesses of the mountain.

History of Discovery

• Novomahlenska River: The cave was officially discovered during extensive speleological surveys conducted along the basin of the Novomahlenska River in the year 1974.
• The Discovery Team: The credit for unearthing and documenting these hidden chambers belongs to the researchers Filchev and Andreev, who were actively assisted by local volunteers from the town of Peshtera.

Unique Subterranean Fauna

Yubileyna Cave stands out for its highly specialized troglobitic ecosystem. Its unique fauna was meticulously documented by the world-renowned Bulgarian biospeleologist Petar Beron during research expeditions in 1973 and 2005. Inside the dark, humid galleries, rare invertebrate species have been isolated and identified, including:

• Lithobius lakatnicensis – a specific type of cave centipede belonging to the class Chilopoda.
• Lithobius stygius – another rare centipede species highly adapted to permanent life in total darkness.