Seattle/Tacoma (Washington State) are interlocking cities. Tacoma was born as a Seattle suburb. When you travel to either one, it is not hard to see that any trip or vacation needs to be lengthy enough to take in the best of both. They are so unique that there is so much that you must see.
Tacoma is a forever changing city, with intense vibrancy and charm. It has an abundance of parks, museums and restaurants that will please even the most finicky traveler. However, the most important attraction is Fort Nisqually, a former Hudson Bay Company outpost.
Seattle by comparison has become well-established. It is especially important to see Discovery Park, the shipping canal/locks, the downtown market and the aquarium.
Of course, no trip to either city would be complete without a visit to their harbors. Both offer dinner cruises dinners and excellent city views. Elliott Bay piers, the local bandstands and an endless array of interesting shops nearby are also enchanting. Seattle's Pioneer Square has a former secret underground railroad that once led slaves to the safety of Canada. However, paid tours are advised because many restorations are being done to repair years of neglect and damage on quite a few buildings.