The Piusa River Landscape Reserve was established to protect the primeval valley of Piusa River and the Devonian sandstone outcrops found here and spreads over the parishes of Meremäe, Vastseliina, and Orava. The valley of the river is a 35 m deep and 300 m wide primeval valley cut into sandstone. The hydro energy of Piusa River was previously used to operate 11 mills. The buildings of the watermills of Kelba, Tamme, and Väike-Härma are standing to this date. The greatest treasure of the landscape reserve are the 12 Devonian sandstone outcrops of the heights of 6-44 m and lengths of 20-130 m with the tallest known as the Härma walls. We recommend hiking by the 15-kilometre Piusa hiking trail to get acquainted with the Piusa River Primeval Valley Landscape Reserve.