Tiirismaa Hill and Pirunpesä Gorge, Hollola

Tiirismaa Hill in Hollola is the highest point of Southern Finland. It consists of quartzite, sedimentary rock that originated in the quartz sand accumulated at the bottom of a shallow shore about 1 850 million years ago. The monumental Pirunpesä Gorge has been a well-known visitor attraction since the 1800s. It is a cliff fissure formed along a weakness zone in the Tiirismaa bedrock, where over the course of time the stone has fractured and broken up. The gorge formed when the glacial meltwater burst through via the weakness zone in the bedrock and flushed the gorge of loose material. So-called ripple marks can still be seen in the boulders and cliff faces of the gorge – these are patterns left by ancient waves in the seabed sand.