Following years of debate, Seattle is doing away with its elevated highway structure - the Alaskan Way Viaduct - and replacing it with a tunnel. The earthquake-vulnerable section of State Route 99 runs north-south, sitting between downtown Seattle and the waterfront.

As the project began on a rainy Saturday morning, the city allowed people three hours to walk atop the old highway.

More coverage from the Seattle Times and seattlepi.com.