Jus starting with the most recognizable symbols of the area you have the Space Needle and Monorail built for the 1962 Worlds Fair, then you add/adapt sites like the Capitol building in Olympia (already nice Federal style architecture), University of Washington, Ballard locks and Elliot Bay, the bus tunnel under the city, I-5 freeway covered over by Freeway Park and the Convention Center, Boeing Field, Payne Field, Nike Site Hill, Fort Lawton, the former Sand Point NAS, lots of nice bridges over water and between hills, floating bridges (which may/may not be floating anymore - or floating in quite the way they were named for) etc.
Nearby you have US Naval Station Everett, McChord AFB, Fort Lewis, Puget Sound Naval Shipyard, Bangor Strategic Weapons Facility (that's nuclear missile submarines and associated warhead storage), Whidbey Island NAS, Tulalip, Muckleshoot and Nisqually Indian Reservations, McNeil Island Federal Prison, rivers, lakes, hills and mountains.
Yeah, I lived there most of my life and I could see the area adapted as a Fallout setting VERY easily. The longer I think about it the more spots in the area I think of that would fit.
It's diff got all the right elements.