Tilleoru landscape reserve is one of the oldest reserves in Põlva County as well as in Estonia.
Tilleoru primeval valley is on average 0.5 km wide and up to 35 metres deep. The floodplain is full of springs. There is a sandstone outcrop on the banks of the Ahja River called Merioone cliff. Merioone spring flowing out of it gives out 16-23 litres of water per second. People believed that the spring was connected with the sea and therefore it was so extraordinarily rich in water. The visitors can see interesting nature sights on the 5-kilometre-long nature trail.