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Photo: Ahmet Baris ISITAN, CC BY-SA 3.0 via Wikimedia Commons
Remarkable complex of caves, 3 km in total, of which you visit 450 m, wear stout shoes. There are three caves of strikingly different appearance. You enter through the lowest, sulu mağara or "wet cave", where a sidewalk follows the creek – in winter this cave floods and is closed. Dripstones are still forming down here. After 250 m only experienced cavers may go deeper, and the bats do as they please, while visitors ascend 60 m on the steps to kuru mağara or "dry cave". This area is richly decorated with stalactites and stalagmites, and you explore 200 m then exit. The third cave kız or "maiden" is also on this level, but closed to tourists: you wouldn't want to disturb 60,000 bats. As to the name "Dupnisa", a fey legend invokes Dionysos, but it's just Bulgarian Дупница (dupnitsa) which means "hole".
The Dupnisa Cave, aka Dupnisa Caves, is a show cave located in Kırklareli Province, northwestern Turkey, close to Bulgarian-Turkish border. The cave itself, unlike what the original name suggests, is actually three, interconnected caves divided into two separate floors. Its name is derived from the Bulgarian word Dupnitsa (Дупница), related to the word for "hole".
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A well-preserved historic village over the hills.
Demirköy Dökümhanesi
This is a foundry and industrial village established in the 15th century to process the local iron and copper ores. There's a mine within the complex, plus accommodation and a mosque for the workers. A canal supplied a waterwheel which pumped bellows for the furnaces. Iron from this foundry was taken to the coast at İğneada and transported to shipyards and to the Imperial cannon factory – it found its way into cannonballs fired during the Ottoman capture of Istanbul in 1453. The foundry was renovated in the 19th century but wrecked in the Russian invasion of 1877/78; after the Great War it was abandoned.