It could be a very fun trip for you, but we need to know a little bit more information to be helpful.
How long?
Adults only or with kids?
Need to be close to a certain area or venue? and where in relation to Downtown Seattle?
The one thing I would recommend is taking a Ferry Boat ride from the waterfront to Bainbridge Island and then maybe stop for some lunch there and come back.
It provides a few hours of entertainment with a great view of the city from the water and gives you a chance to just chug along on a boat for a couple of hours and see the sights, smell the air, look at things and not have to drive.
On the waterfront are several options for food, shopping, sightseeing and such.
Tell us a couple of details.
TIME counts on a vacation!
I've lived in Washington my entire life, most of it in Seattle.
I live in Bellevue now and dislike Seattle with a passion...but, for a visitor, depending on their constraints, it could be a LOT of FUN!
(BTW, staying in Bellevue and then getting to and from Seattle via I-90 could also be an option. It would require renting a car and dealing with parking, though. )