The beginning of the Bronze Age in Estonia is dated to approximately 1800 BC. The development of the borders between the Finnic peoples and the Balts was under way. The first fortified settlements, Asva and Ridala on the island of Saaremaa and Iru in Northern Estonia, began to be built. The development of shipbuilding facilitated the spread of bronze. Changes took place in burial customs, a new type of burial ground spread from Germanic to Estonian areas, and stone cist graves and cremation burials became increasingly common, alongside a small number of boat-shaped stone graves.