Marathon Key, Florida has a curious story behind its name. It is said that the area got the name as the laborers, working hard to complete the railroad project complained that the project is going to be a real marathon. The local station along the railroad was later named as Marathon. The region has been labeled as the unofficial heart of the Florida Keys. Guest at the Marathon vacation homes and rentals can spend their time scuba diving, snorkeling, sailing, fishing, hiking, or biking. 
Never miss Crane Point Hammock, a 63.5-acre land tract that is one of the most important historical and archaeological sites in the Keys. The area contains evidence of pre-Colombian and prehistoric Bahamian artifacts, and once was the site of an entire Indian village. On site are the Museum of Natural History of the Florida Keys, an archive of ancient artifacts including remnants of pirate ships, a bellarmine jug dating back to 1580, and a 600 year old dug-out canoe. 
If you have ever wanted to touch, swim, or play with dolphins, the Dolphin Research Center, located at mile marker (MM) 59, is the place to be! The shores of Sombrero Beach are ready for you with shallow and deep water swimming for the entire family. It is the largest beach in the Upper and Middle Keys. If you are not swimming, try some beach volleyball, or retreat to the tiki huts for relaxing in the shade. Don't forget to visit Pigeon Key, a tiny five-acre island nestled below the old Seven Mile Bridge, if you have a passion for history.