Diablo Lake, Reservoir in North Cascades, Washington, US.

Diablo Lake is a reservoir at 366 meters elevation in the Skagit Valley, stretching between mountain slopes and conifer forests of the North Cascades. The water glows in a turquoise tone created by fine rock particles from surrounding glaciers.

The dam was built in 1930 as part of a hydroelectric project on the Skagit River to supply electricity to Seattle. The flooded river section formed the present body of water, one of three reservoirs in this valley.

The name comes from Diablo Dam, which altered the river's natural path to form this body of water. Today, boats carry visitors across the reservoir while hikers stop along the shore to take in views of the surrounding peaks and the colored water.

The Diablo Lake Trail is a moderately difficult 7.6-mile (about 12 km) hike that climbs roughly 1,300 feet, passing through forest and offering viewpoints over the water. Sturdy footwear helps on the climbing sections. Two-pole fishing is prohibited on the lake.

The color forms from suspended rock particles that glaciers have ground over centuries and that continue to enter the water. Even on cloudy days the water keeps its notable tone because light refracts through the suspended particles.