Stone mushrooms are a quirky natural phenomenon in the valley of the River Sotera. The natural sculptures, resembling mushrooms with a 5 to 6-metre-high stalk, mostly made of clay, are topped with large stone caps. These mushrooms appear because the soil is washed and weathered out from under the stone. There were three of them until 1983, but the tallest one, named the Watcher of the Clearing, has been destroyed. In 1999, three smaller mushrooms were found, but they have only begun to take shape.