Near Salantai, in the wide and marshy Erlos Valley, at the confluence with the Alkupis River, stands a huge moraine hill, the southern part of which is called Alkos kanu (less commonly – Aukos kalnas, Šventimų kalnas). In its northwestern part, there used to be an old oak tree called Šventuoju (cut down in 2003). Nearby, at the foot of the hill, lies a ceremonial stone with a hollow, called Aukuro akmuo (Altar Stone), and a spring gushes from the high slope, flowing towards the Alkupis River, which flows along the southwestern foot of the hill. It is believed that in the 1st millennium–first half of the 2nd millennium, an alka (ancient Lithuanian word for "sacred place") operated on the hill, a temple of the ancient Lithuanian faith, which was renovated in the second half of the 16th century–early 17th century during the conflict between the Protestant Reformation and Catholicism. It is said that the temple was located in the western part of the hill, where a sacred fire burned on an altar stone under a thick oak tree, guarded by priestesses, and a priest lived in a hut built among old oak trees. The temple was dedicated to the god Pilvyčius (Pilnyčius), and the priestesses fed and raised the snakes kept there on the hill of Gaidžio kalnas in the Salanto Valley. Sacrifices to the gods were made under the Holy Oak. The spring water has healing properties and is mainly used to treat eye diseases. The priestesses of Alkos Hill were the longest in Samogitia to prevent the eternal fire from being extinguished: without weapons, they poured ashes into their aprons and defended themselves from soldiers who came to extinguish the fire by throwing ashes into their eyes. Once the fire was extinguished, they disappeared into thin air. After Christianity became established, on Midsummer's Eve, young people from the Salantai area would light bonfires on the altar stone. At the beginning of World War II, gravel began to be dug from the southeastern end of the hill for the village road. It is said that people found bronze jewelry, stone balls, and other artifacts in the gravel pits. When a human skull was found, the work was stopped, and a roofed pillar was erected on the hill. Folklore has preserved many different legends about the hill. They say that in ancient times, the hill was an island in the middle of a lake, which later dried up and turned into a meadow. The hill was built by Swedish soldiers who settled here and plundered the surrounding area. The angry women of Samogitia killed them. As they were leaving Lithuania, the Swedes buried gold in the hill and planted an oak tree there as a sign. It is said that there is an ancient church inside the hill, which can be reached by an underground passage. It is explained that the name Alka comes from the fact that people were left here without food to starve to death, and that the hill is called Alka because the people surrounded by the Swedes died of starvation here.