The stone mushrooms are rock formations, located east of the village of Beli Plast, at the road, connecting Kardzhali with Haskovo. The protected site has a total area of 3 hectares. It was declared a natural landmark by Order No 1427 of 13 May 1974.
The rock formations have the shape of natural mushrooms – their stalks are pink, and the caps are green. The height of the mushroom stalks and the width of the caps are up to 2.5 meters. They are made of rhyolite volcanic tuffs, which are the result of intensive underwater volcanic activity, dating back to the Paleocene. After the sea withdrawal and the consistent seabed rising, the influence of the erosion became visible. The lower, pink layer proved to be softer and more amenable to the effects of sun, wind and rain. The upper, green layer contains solid minerals, mainly volcanic glass and it is therefore, more difficult to weather. So a wonderful combination of unique shapes and colors has formed over the millennia.
According to a legend, the charcoal-burner Raduil lived in the Perperikon fortress with his four beautiful daughters. One sunny morning they went outside the town walls to bring water. Suddenly, they saw a great horde of invaders at the hill near the river. They ran back to the fortress. A fervent, uneven battle started; many men were killed, most of the women were captured. The daughters of Raduil were among them.
They were waged to the leader of the horde, astride a racial horse at the nearby river – to take a look at them and choose the most beautiful ones for him and to sell the others as slaves. Fury gripped the hearts of the girls as they approached him. They grabbed what they could – sticks, stones, and began throwing them at the rider. The horse got scared and stood on its hind legs. The unsuspecting rider fell on the ground, the four girls ran towards him and tore him apart and ran into the forest.
The closest friend of the leader ran to pursue the girls and caught them at the end of the day, lashed out with his yataghan and cut off the first one’s head. As it fell on the ground, it turned into a stone mushroom. The same happened with the other sisters. Before the man cut the head of the last girl, she petrified. The terrified man tried to escape with his horse but turned into a black rock at the first step. Nowadays people call the lonely rock near the mushrooms Karatepe.