Pobiti Kamani Stones

Located near Varna, these unusual hollow columnar rock formations look like the remains of an ancient forest, but they are not. The mysterious Pobiti Kamani, or "upright stones", can be as large as 30 feet tall and there are several theories on how exactly they came to be. One current theory is that they are built up mineral deposits surrounding natural methane vents in the ground.

Unique in the world, the area is now a designated UNESCO World Heritage Site. The only similar formations known are in Shark Bay and Nambung National Park, Australia.