The Devetashka cave is located near the village of Devetaki and is one of the largest caves in Bulgaria. Among the locals it’s also known as "Maarata" or "Oknata" for its seven different-sized holes in the ceiling where light enters and illuminates the central hall. Studies found that the Devetashka cave has been inhabited during almost every historical period. The earliest evidence of human presence dates back to the Stone Age - 70,000 BC. In Roman times a sanctuary was built over the small spring in the great hall and a plate of the Greek hunting and fertility goddess- Artemis was found among its remains.

The entrance of the cave is 35 m. wide and 30 meters high and has a semi-elliptical shape.  A spacious hall with an area of 2400 m2 is set 40 m. deep and it is considered the biggest cave hall of the Balkans. At the bottom, the hall lit by the seven holes, separates in two sections. A small creek, which flows into the Osam River, runs along the first fork and the other ends in a small gallery, known as the "Altar".

Today the cave is home to various species of winged mammals and is one of their three biggest habitats.