U.S. Route 1 through the Florida Keys is as much an engineering marvel as it is a major highway. Built atop a former railway bed, the 127-mile Overseas Highway crosses dozens of bridges and at times seems to simply hover above the brilliant blue water below. It's prone to congestion, and speed reductions protect the endangered Key deer, only around 30 inches tall. But there are plenty of diversions before you reach the highway's southern terminus in Key West, like diving and snorkeling off Islamorada, or kayaking around the beaches of Bahia Honda Key.
Updates via