In this incredible video that includes both real-time and timelapse footage, we see the Condit Dam (built in 1913) being drained for the final time as the project to decommission and remove the dam commences (October 26, 2011).

The reservoir draining took about 2 hours and was the first step in restoring the White Salmon River in Washington, USA. Condit Dam was the largest dam ever removed in the United States until the Elwha Ecosystem Restoration Project on the Olympic Peninsula removed the larger Elwha Dam and Glines Canyon Dams. [source]