The park contains over 9,000 recorded sinkholes within its territory.
Karvės ola (Cow’s Cave) is approximately 10 to 12 meters deep and reaches 10 to 12 meters in diameter.
The regional park was established specifically to preserve the unique karst topography and the ecological integrity of the Mūša-Nemunėlis lowland.
Biržai Castle houses the Sėla Museum, which maintains a collection regarding the history of the Biržai Duchy.
The Kiručiai mound is one of several archaeological sites preserved within the park's administrative boundaries.
The groundwater chemistry in this area is heavily influenced by gypsum dissolution, resulting in highly mineralized water.
Biržai Regional Park is located in a unique karst landscape area in northern Lithuania characterized by active sinkhole formation. The park is home to the Cow’s Cave (Karvės ola), a well-known sinkhole that continues to evolve due to underground limestone dissolution. It encompasses the historic Biržai Castle, which features a reconstructed 17th-century bastion fortress. The region is famous for its long-standing beer brewing traditions, recognized as a form of cultural heritage. Landscapes feature diverse wetlands, the Agluona and Apaščia rivers, and numerous smaller dolines. The park serves as a research site for geologists studying active geological processes in the Biržai Karst Region.
The wooden footbridge spanning Lake Širvėna provides the best view of the castle and the surrounding park landscape.
Wear sturdy, closed-toe walking shoes as the terrain around sinkholes can be uneven and soft.
Bring mosquito repellent, especially when exploring the wooded areas or near the lake shores in summer.
Visit the visitor center at Rotušės g. 10 first to obtain a current map of accessible sinkhole trails.
Do not attempt to walk off-trail in karst zones, as hidden smaller sinkholes may be obscured by vegetation.
Museum exhibits within the castle may have restricted access during winter months; outdoor park trails are accessible year-round.
Do not enter the bottom of sinkholes, as the soil remains unstable and collapse is a documented risk.
