The Leavenworth area is one of the most popular bouldering regions in the Pacific Northwest. The rock is granite, with a grain somewhat larger than that of the Skykomish Valley boulders, but the terrain tends to be flatter and the environment drier.
There are classic problems of every grade here, and although the boulders themselves are spread out along the two canyons there are almost always plenty of problems within walking distance of a given road pullout.
Leavenworth is a faux-bavarian tourist trap surrounded by high quality sport and trad cragging, bouldering, ice and alpine climbing on generally high quality granite. The Leavenworth area is generically broken down into two main cragging areas: Icicle Creek and Tumwater canyons. But these are each composed of numerous sub-crags, and surrounded by bouldering and amazing alpine areas. Classic areas include Castle Rock in Tumwater, Careno Crag in Icicle, Snow Creek Wall, Mt. Stuart and the Enchantments.
Rest days include whitewater kayaking and rafting, oggling tourist chicks, guzzling brews on a sunny terrace in town, or hiking into the Enchantments, one of the most amazing alpine environments around.
To get to there from Seattle, take I-5 to Highway 2 and follow it over Stevens Pass to the town of Leavenworth, or take I-90 to Highway 97 and head north to Highway 2, then bank west.
Just a quick note that I've recently written a bouldering guidebook to Leavenworth and Gold Bar. It's called Central Washington Bouldering, and contains over 500 problems in Leavenworth and roughly 150 in Gold Bar. The easiest way to get the guide at this point is to purchase it directly from the publisher at their site: www.sharpendbooks.com/prod.php?t=1&q=WA