‘America’s Southernmost State Park’ is home to an impressive fort, built in the mid-1800s, that played roles in the American Civil War and in the Spanish–American War. The beach here is the best one Key West has to offer – it has white sand to lounge on (but is rocky in parts), water deep enough to swim in and tropical fish under the waves. It's also a fine spot for sunset viewing. Learn more about the fort on free guided tours offered at 11am.
There's a fine cafe on-site, and you can hire lounge chairs and umbrellas, as well as snorkeling gear for aquatic activities. If coming by foot, it's about a half-mile walk (12 minutes) from the entrance to the beach.
