The Natural Phenomenon Stone mushrooms (aka Rock mushrooms ) is located about 1 km north of the village of Beli Plast , up to the road between Haskovo and Kardzhali . Local people call it Mantrakaya .
Mushroom shaped rock formations are sculpted into rheolite volcanic tufts. The pink color is due to the mineral clonopilolite, and the blue and black spots are from manganese congeners. A greenish bar comes from the Salononite Mineral Salt. The rocks themselves are up to 2.5-3 m high.
The area of 3 hectares in which the rock formations are located was declared a natural landmark on 13 May 1974 under Order No RD-552 of the Ministry of Environment and Forestry. In the protected area, interesting bird species can be observed: Eagle Squirrel , Egyptian Vulture , Red Swallow , Spanish and Common Wheatear .
