Arctic Circle level, although in mountainous regions there is often no direct view of the true horizon. Only four million people live north of the Arctic Circle due to the severe climate; nonetheless, some areas have been settled for thousands of years by indigenous peoples, who today make up 10% of the region's population. Tens of thousands of years ago, waves of people migrated from eastern Siberia across the Bering Strait into North America to settle. The largest communities north of the Arctic Circle are situated in Russia, Norway and Sweden: Murmansk (population 307,257), Norilsk (175,365), Tromsø (71,295), Vorkuta (59,231) and Kiruna
Arctic Circle (organization) issues facing the Arctic as a result of climate change and melting sea ice—such as oil and gas exploration, environmental concerns, national security, and the effects on indigenous populations—as well as the growing international interest in the region. With the opening of shipping lanes and other economic activity in the Arctic, the organization says, the region "is moving to center stage and is playing a significant role in issues such as globalization, economic development, energy exploration, environmental protection and international security." The Arctic Circle held its first open assembly October 12–14, 2013, in Reykjavík, Iceland, at the Harpa Reykjavík Concert