We've done Turtle Bay as a day trip, but to get the most out of your visit you might want to plan a weekend away and combine Turtle Bay with a visit to Shasta Caverns, also in the Redding area. Or make it three or four days and spend some time on Lake Shasta, too.
Turtle Bay is a pretty good sized complex that features permanent and traveling exhibitions. This was a home for the "Art of the Brick" Lego exhibit as well as "Grossology," both of which...