My wife and I took a tour bus from our hotel and made it a small day trip out of it. When you really learn about how this thing was built, it is a man made marvel. It's really something everyone should see once in their lifetime. Just be warned, before entering the tours or inside the visitor center, security there is like at the airports. They will run you through a metal detector and wand. So for you terrorists out there, don't even think about it!
P.S. eat something before you get there. Everything they sell there is SUPER UBER expensive and probably doesn't taste that great for the price.