In Biržai region, people avoid uttering a common swearing expression: ‘Kad tu prasmegtum!’ (Literally: Be swallowed by the Earth) even to a foe because it may come true... Circulating ground water may dissolve gypsum, sandstone, or dolomite bedrock, gradually forming spaces and caverns known as karst sinkholes. The total number of sinkholes in the district is estimated to be more than 9,000 and the number is still increasing.

Karajimiškis Landscape Reserve is situated around 3 kilometres west of Biržai. This area is unique because of the highest density of sinkholes (more than 200 items per sq. km). The reserve boosts the most famous and largest sinkhole in Lithuania, called Cow’s Cave(Karvės Ola). The story goes that once a cow was swallowed by the earth leaving only a stub of its chain at the rock. The Cow’s Cave is a funnel-shaped, almost round sinkhole. According to speleologists, it appeared around 200 years ago. It is 10-12 metres in diameter and around 12.6 metres deep. An opening is at the bottom of sinkhole. At the depth of 9 metres, there are five branches (WetCave, Narrow Hole, Bat Hole, and Toad’s Cave) and a lakelet 1.5 metre deep. The Cow’s Cave is still actively developing. Its parameters, the length of holes, the form of sinkhole, and other cavities are changing.

Karajimiškis landscape reserve is rich in many other famous sinkholes such as Geologists’ Hole (Geologų duobė), Fox’s Cave (Lapės duobė), Eve’s Hole (Ievos duobė), and Easter Hole (Velykų duobė).


Kirkilai Landscape Reserve (1,137 hectares, 8 kilometres north-west of Biržai) is an area of active surface karst formations. Lakelets of Kirkilai are a renowned scenic attraction in this reserve full of sinkholes. A circular lake indicates that the lake evolved from a collapsed sinkhole. When a sinkhole collapsed to expose the water table at the surface, the sinkhole was filled with water forming a small circular lake. The group consists of more than thirty interconnected small circular lakes covering more than 4 hectares in total. Northernmost, a lakelet called Pike’s Pit (Lydžio duobė), which appeared in 1915, is only around 50 metres long but up to 11 metres deep. 

The lakelets are renowned for their twisted shorelines, picturesque peninsulas, isthmuses, bays, and islands. The group of lakelets of Kirkilai is the only one of the kind in the Baltic region.

Interestingly, species of fish such as ides, which usually prefer large rivers and lakes, are found in the lakelets of Kirkilai. Supposedly, there are underground tunnels connecting lakelets to rivers.

Biržai Regional Park: