The Muddy Volcanoes are located in Berca, Buzau County. Since 1924, this surface with an area of 30 km² (12 square miles) has been declared a nature reserve. The main attraction of the protected area are small mud volcanoes, which are a few centimeters high. Volcanoes are created by gases that rise from a depth of about 3,000 meters through clay and layers that contain water. The mud dries on the surface of the earth and forms structures that look like a volcano.