Incredible Drive Above the Trees - in WASHINGTON state, about two miles west of the summit of Snoqualmie Pass on Interstate 90 through the Cascade Mountains; it is a 20-span, 3,630 feet long viaduct across a steep, forested slope, a deep ravine, and an avalanche path
THE WORLD GEOGRAPHY: 6 Incredible Drives Above the Trees
The Underground tours!!! So cool and spooky. Not sure about this particular company, but in general totally worth doing. Underground opium dens, prostitution, speakeasies and shanghaiing (see : http://en.wikipedia.org/wiki/Shanghaiing).
UNDERGROUND TOUR - Seattle's Underground Tour - No Heels!