Just go see the damn Dam! Worth the price of admission. This is definitely a place to visit if you have a little time to go while in the area. I came here with my family after a trip to Las Vegas and it was really worth the extra drive to the Hoover Dam. You get a gorgeous view of the Nevada/Arizona border against the backdrop of the beautiful blue water & sky. The scenery is really amazing.
The actual tour is very informative and they take you down to the area where you can see the entire structure holding all of that water back. And on the other side-- Lake Mead & the Colorado River. Unfortunately, you don't actually get to touch the water which would be pretty cool on a hot summer day.
Overall, I highly suggest making a little side trip if your heading to Vegas or you're in Arizona, because it's so worth seeing how big it is and parting with the money spent taking this tour.
Just do it.