Just past Boulder city on Hwy 95. 'Opted for the mini tour as the next full tour was about 3 hours from when we arrived. The tour guide was very knowledgeable and had a loud enough voice to engage all of us who took the tour... About 30-45 people. It cost $10 for parking and with a military discount, the shorter tour was $12 each. We watched a short film about the building of the dam and proceeded to go via elevator 54 stories under the dam. Our ears were popping as we descended. You could definitely feel the difference in cooler temperature down below in the caves. We learned that the workers back in the 30's made $4 a day, and if they called-in sick, they lost their job. The electrical turbines were huge and because it was the weekend, they only had 2 generators working. The high water mark was made during 1983 when the snow runoff filled lake Mead. Apparently, there are two buried towns of which one is supposedly visible. I didn't see it. The dam supplies 7 states with energy but does not supply the casino corridor in Las Vegas. The dam straddles the Arizona/Nevada border. This is a federal security site with check points and x-Ray screening like an airport. No knives or fire arms permitted. The gift shop had your usual fare of souvenirs and though we did not patronize it, they also sell food. Only about 30-45 minutes from the Las Vegas casino corridor. A once in a lifetime event. I had a great time. The employees were friendly and helpful.