After being bored to tears at Art in the Park, we decided to go to the dam which is just a few miles from Boulder City. You just have to see it in person to appreciate it. The water is a bright blue color and the canyon with the electricity lines looks like something out of a Ratchet and Clank game.
Park on the Arizona side where there are several small lots to park for free and walk across the dam back to the NV side. Bring a sun hat or an umbrella on hot days. There isn't much shade.
Make sure to check out the bathrooms on the dam itself. Outside they look like an art deco era elevator bank. Inside the stalls also look like to be from the early 1930s. Clean though.
Don't forget to walk along the bridge above it all to take in the views.