Some think of the Florida Keys as an emerald necklace of American ecological gems, while others see it as a superhighway cruise ship. A Florida Keys vacation can include charming Key West hotels and a Florida Keys dive to subtropical reefs or fishing Florida Keys tarpon.

Geographically, the Keys are separated into The Upper Keys, the Middle Keys, and the Lower Keys. Along the way, these include Key Largo, Marathon Key, Bahia Honda Key, Big Pine Key, and Key West.

Less than a century ago, the Keys were unreachable except by boat. In 1912 Henry Flager built a railroad to Key West, connecting to his steamship trade with Havana, only 90 miles further. The railway washed out in a 1935 hurricane, but three years later was reborn as the Overseas Highway, which today connects more than 30 of the populated "mainline" keys.

The hundreds of remaining undeveloped islets are known as the "backcountry." In 1990, Congress established the Florida Keys National Marine Sanctuary over 2,800 square nautical miles of coastal waters. These marine environments include sea-grass meadows, mangrove islands, and one of the only living tropical reefs in North America. These fragile environments support sponges, anemones, jellyfish, crabs, rays, sharks, turtles, snails, lobsters, and thousands of types of fish.

At the top of the chain is Key Largo, only an hour’s drive from South Florida’s two major airports. This “Diving Capital of the World” is home to one of the best diving sites in the world, John Pennekamp Coral Reef State Park. The 78-square-miles marine park features 40 species of living coral and 650 varieties of fish. The visitor center features floor-to-ceiling aquariums. Amenities include glass-bottom boat trips to the reef. At the Florida Keys National Marine Sanctuary you can dive to the wreck of the Spiegel Grove, a 510-foot Navy ship intentionally scuttled to start a new coral reef.

The “Sport Fishing Capital of the World,” Islamorada makes fishing Florida Keys for sailfish, tuna, tarpon, and bonefish all in one day a possibility.

Marathon calls itself "The Heart of the Keys." Sombrero Beach is the largest and nicest beach in the Keys, with picnic facilities, a playground, and a protected cove for kids. Marathon holds the annual Seven Mile Bridge Run. Parallel to the Overseas Highway between the Middle and Lower Keys, the Old Seven Mile Bridge, on the National Register of Historic Places, includes a 2.2-mi segment is open for biking, walking, and rollerblading.

The beautiful Bahia Honda State Park and Recreation Area has a 2.5-mile stretch of sand that tops “best in America” beach lists. Activities include swimming, fishing, kayaking, biking, snorkeling, and hiking on the Silver Palm Trail.

Big Pine Key is home to the National Key Deer Refuge, as well as a great place to charter a Florida Keys dive cruise.

At the end of the road, Key West was once home to John Audubon, Ernest Hemingway, and Jimmy Buffet. This tiny laid back “Conch Republic” now gets 1.6 million visitors a year.