Boulder Canyon Dam (or Hoover Dam). Since 9-11, you have to stop and to through a security check prior to getting close to the Dam. I was pulled over because of the bike trailer and they made me open and inspect inside. Nothing like going into Canada last summer, this guy was very friendly and it only took a few minutes. And, the let SAG wait along side while he inspected. It did take over 30 minutes to get across due to traffic and construction.