Dupnisa Cave is in the town of Demirköy and located 6 km far from south west of the village of Sarpdere. It is 230 Kms far from İstanbul.
It is predicted that, the cave formed during the second geological time nearly 180 million years ago. Dupnisa Cave, Thrace's first and only cave which was offered to tourism, is in a region where Rezve Stream which chapped Istranca Mountains and formed canyons and which forms Turkey-Bulgaria border and with a wild view.
The area is under preservation.
Total lenght of Dupnisa Cave which is considered of two layers and three caves having different developmental features is 2720 meters. Hydrological features, developmental stages, fauna density, meteorological features and in-cave dripstone deposits of the three caves which developed through a height of 70 meters are extremely different from each other. Having three caves in contradiction one on the top of other is very interesting. Kuru Cave (Dry Cave), which is on the top, is very rich in terms of dripstone deposition. Especially stalactite, dickite, column and wall dripstones are huge. On the other hand, Sulu Cave (Wet Cave), under the former, has underground streams and lakes ; wall and curtain dripstones fall down on those streams and lakes like fringes which make the cave interesting.
In the Kız Mağarası (Maiden Cave) approximately 60.000 bats from 11 species spend the winter period. For the reproduction of those bats, the “Maiden Cave” is closed to the visitors between November 15 and 15 May every year but the “Dry Cave” is opened to the tourism throughout the year.
Thus, the system which formed by Kuru (Dry) and Sulu (Wet) Caves is quite suitable for tourism. Additionally, natural beauty increases the touristic importance of the cave. Especially in summer, it is flooded by thousands of visitors.
Dupnisa Cave is from one of the well-known caves of Turkey with its natural beauty, streams, groundwaters, lakes and living creatures. From the colour of white to the red and brown, giant stalactites, stalagmites and columns can be seen in the cave.