The largest karst area in Lääne County is just a few kilometres from Linnamägi, in the direction of Sutlepa. It is around 600 metres long and 100 metres wide. Around 1.5 kilometres of Salajõgi River flows into Haapsalu Bay below ground. Its source is in the springs south-west of the road, from where it flows as the Tiberna River. During dry periods, only a few litres of water per second flows in Salajõgi River. During high water, however, the water reaches the highway, filling the karst valley and forming a lake. There are two large Gneissbretsa boulders just off the Salajõe–Ingküla road, called the Kasemetsa and Allika Boulders. The largest of the two stands 3.9 metres tall, while the smaller stands 3.4 metres tall.