An engineering marvel. What makes it more spectacular is a project like this would never see the light of day in today's world. There is too much bureaucratic red-tape, fanatical tree-huggers, and impending cost over-runs. As a former SoCal resident, I am glad we built it (and the Calif Aqueduct).
I took my Mom and aunt to do the tourist thing, turned out that I enjoyed it way more than they did. Definitely a must see, but not in the middle of summer, it gets VERY HOT.
Spongebob says if you pay for the Premium Tour package, you can see the "Megatron" model they used in Transformers the movie! Really!