Guide
Dupnisa Cave lies within the bounds of the village of Sarpdere in the Demirköy district of Kırklareli, five to six kilometres south-west of the village. It is the only cave in Thrace open to visitors.
The cave is an underground system on two levels with three entrances, 3,150 metres long in all. On the upper level are the Maiden's Cave and the Dry Cave, both of which have finished forming. Fifty to sixty metres below them lies the Wet Cave.
The Wet Cave is entered through the Dupnisa doline. It runs 1,977 metres, of which a thousand metres hold water, and its far end lies sixty-one metres above the entrance. The spring issuing from the cave forms the Rezve stream, which marks the Turkish-Bulgarian border.
The Dry Cave begins at two separate entrances and has branches of 456 and 363 metres. The first entrance lies a hundred metres south-east of the Dupnisa entrance and takes the form of a vertical shaft five metres deep; the second is twelve metres lower and 225 metres to the south-east. One branch of the cave connects to the surface through a shaft, while the other joins the Wet Cave. Wall formations and stalactites and stalagmites are abundant here.
The third entrance is that of the Maiden's Cave, which begins on a slope of sixty degrees. Its side branches are fossil while the main system is active, and it holds a chamber measuring 150 by sixty metres. Because of the great number of bats it is closed to visitors.
Two hundred metres of the Dry Cave and 250 metres of the Wet Cave are open to visitors. The Maiden's Cave is closed between 15 November and 15 May while the bats are breeding.
Most of the bats are in the Maiden's and Dry Caves, and cave butterflies and cave flies are found here as well. A count made in 2001 recorded thirty thousand bats of eight species.