After the Ice Age, at around 8,000 BC, there had already been vast migrations towards the present-day Stockholm area, but as temperatures dropped, inhabitants moved away towards the South. Thousands of years later, as the ground thawed, the climate became tolerable, and the lands became fertile, some life moved back to the North. At the intersection of the Baltic Sea and lake Mälaren is an archipelago site where the Old Town of Stockholm was first occupied in about 1000 AD by Vikings. Vikings had a positive trade impact on the land because of the trade routes they created.