The Nabala-Tuhala Nature Reserve is located in Kiili, Saku and Kose Municipality in Harju County and Kohila Municipality in Rapla County. The protected area covers 4628.7 ha.
The protected area includes extensive karst areas with eight underground rivers. The valleys, streams, depressions, lakes, swallow holes and springs above the subsurface stream form a diverse karst landscape. A well-known and unique sight is the Tuhala Witch’s Well, which overflows in periods of high water.
Its peculiar hydrological regime and significant annual water level fluctuations have resulted in species-rich spring fens, fens, paludified forests and deciduous bog forests, which are highly sensitive to drainage. Areas in their natural state or with little drainage impact provide habitats and breeding grounds to several endangered and protected species.
The karst areas of Tuhala and Nabala belong to the list of objects of primeval nature of Estonia. The Rahaaugu, Tammiku and Tuhala special areas of conservation, which are part of the protected area, belong to the Natura 2000 network.