Close to the smallest town in Bulgaria – Melnik, are located the Melnik Pyramids – one of the most interesting natural attractions in the country. They are rock formations, which are located on an area of 50 sq. km. They are beautiful sandstone formations, in some places completely vertical, with grasses and deciduous trees on the tops and possessing high aesthetic value. In addition to their pyramidal shape, they are also shaped like mushrooms, cones, needles, etc. It is believed that the pyramids acquired their shape by erosion of the clay soil. The Mill Pyramids are in the process of being shaped and their appearance and shape have changed over time.