North Central Baltic

These waters lie off Hiiumaa, or Dagö, in the West Estonian archipelago. A major east–west route across the Baltic passed the dangerous Hiiu shoal, and Hanseatic merchants sought a landmark to guide their vessels. After the bishop of Ösel–Wiek gave permission, a massive stone tower was erected on the island's Kõpu peninsula and completed in 1531. Hiiumaa itself belonged to Sweden from 1563 until the Treaty of Nystad transferred it to Russia in 1721.