Unifying Seattle’s various bodies of water, freshwater Lake Union was carved by glacial erosion 12,000 years ago. Native American Duwamish tribes once subsisted on its then-isolated shores, but 21st-century Lake Union is backed by densely packed urban neighborhoods and is linked to both Lake Washington and Puget Sound by the Lake Washington Ship Canal (built as part of a huge engineering project in the 1910s). Not surprisingly, the lake is a nexus for water-sports enthusiasts – you’ll regularly see kayakers, rowers and sailboats negotiating its calmish teal waters. It also acts as a runway for seaplanes.