The sinkhole is still geologically active, with its shape and size occasionally shifting over time.
Local legend attributes the name to a cow that allegedly fell into the hole, though it serves as a mnemonic for the dangerous nature of the terrain.
The Biržai region sits on a thick layer of gypsum and dolomite, making it uniquely susceptible to these sudden ground collapses.
The hole contains several small cave-like openings at its base, which are remnants of underground water erosion.
The water within the sinkhole is typically high in sulfate content due to the dissolving bedrock.
Cow Cave, known locally as Karvės Ola, is the most famous sinkhole in the Biržai Regional Park, Lithuania. It represents a classic example of active karst topography formed by the dissolution of gypsum layers beneath the surface. The sinkhole measures approximately 10 to 12 meters in diameter and reaches a depth of about 12.6 meters. A small, dark pond usually occupies the bottom of the funnel. The site is a geological monument and is legally protected as a natural landmark. It is situated within the Biržai karst region, an area characterized by hundreds of unstable surface depressions.
The viewing platform at the top of the sinkhole offers a clear vantage point into the abyss.
Stay on the designated wooden walkway to avoid disturbing the unstable ground edges.
Bring mosquito repellent, as the humid, sheltered environment attracts insects in summer.
Combine this visit with other nearby karst formations like the Jurgiškės or Kirkilai sinkholes.
Do not step off the marked paths or over safety railings, as the ground surrounding the sinkhole is inherently unstable.
Do not attempt to descend into the sinkhole; the walls are prone to collapsing, and the ground is fragile.
