I'd lived in Seattle for a couple of years before having the chance to explore 'East of the Mountains.' The everlasting rains of the Pacific Northwest seem like a distant memory when you cross the Cascade mountain range into eastern Washington--from temperate rainforest to semi-desert sagebrush steppe...and rattlesnakes.
This is coulee country--ancient riverbeds from the gushing end of the last Ice Age. Here, at Dry Falls, you can get an overview of a 3.5-mile-long 400-ft.-high cliff that geologists say was once the world's largest waterfall--ten times the size of Niagara.
Just south of here is Sun Lakes, a state park with pretty good rainbow-trout fishing along with campgrounds. Be warned, though--the geology around here is conducive to wind-tunnel effects; your tent may flap loudly through the night...
To get here from Seattle: Go east on I-90 to exit 151 (Hwy. 283) through Ephrata to Soap Lake, then continue North on Hwy 17; about 3 1/2 hours.