The Rocky Reach Dam, Park, Museum and Visitor Center is on highway 97 north of Wenatchee.  Much bigger than it appears from the road, the  natural history museum is immense and well-organized.  Near the generator room is an interesting display of old electrical and radio equipment.  You can watch big salmon working their way up the fish ladder, and have a snack in the cafe.  And if that isn't enough  the gardens, arboretum and play area are lovely.  Well worth a stop-in.

On the web:

6151 State Highway 97a
Wenatchee, WA 98801
(509) 663-7522