Pirunkirkko (translates as Devil’s Church) is an impressive rapakivi granite rock formation in Paistjärvi Area in Heinola. It is a leaning cliff forming a cave that resembles a gigantic lean-to shelter.
The cave formed along a fracture zone at the foot of a cliff consisting of about 1,600 million-year-old rapakivi granite. The continental ice sheet has transported the loose rock material away, sculptured the cave and made the cliff surface smooth. The cave is 40 metres long and 3–8 meters high. According to folktales, local people used Pirunkirkko as a refuge during hostile invasions in the 18th century.
Pirunkirkko can be reached by hiking about 1 km from the Niinilampi parking area. At the picturesque Lake Niinilampi there is a campfire site. In the Paistjärvi Area there are also other trails. From the parking area by Lake Sonnanen, known for its extremely clear water, you can reach trails leading to the beautiful esker of Kuijärvenharju and the Ketturiutta camping site with a sandy beach.
Pirunkirkko is one of the most important rock formations of the Salpausselkä UNESCO Global Geopark.