In the centre of Viljandi, you will find the Central-Devonian sandstone, which is exposed on the southern border of the castle hills. Finding the sandstone outcrop in the castle park is certainly a surprising reminder of the pristine nature amidst the hustle and bustle of the city.
The outcrop has a maximum height of 6 metres and a length of 18 metres. Nearby, there is a spring, where nature lovers have built a nice canopy to protect its source.