Beside its new concrete counterpart, the old Seven Mile Bridge jets into the sea like a giant fishing pier, inviting anglers, walkers and nature lovers to enjoy one of the Florida Keys most scenic and historic treats.

The blue-green panorama of gulf and ocean, dotted with lobster traps and sailboats, is not unlike the setting viewed by passengers traveling on Henry Flagler's Overseas Railroad from 1912 until 1935.

Off the large key north of the bridges is some of the best fishing and sport diving on the continent. And several top resorts offer luxury accommodations - and a centrally located home base in the Keys.

This is Marathon... "Heart of the Florida Keys."

Marathon boasts the conveniences of a modern community - a 58-bed hospital, shopping plazas and the only commercial airport between Key West and the Florida mainland - but retains the charm of its roots as a 19th - century fishing village.

And it's growing as a tourist resort, a phenomenon local officials say is natural.

Before dusk, residents and visitors alike gather at boat docks to survey fishermen's daily catch and often the entree for their evening meal.

Numerous certified charter boat captains take visitors diving, snorkeling, fishing, sailing and touring along the only living coral reef in North America, several miles offshore in the Atlantic Ocean.

For landlubbers, an 18-hole championship golf course is open to members of country clubs elsewhere, with proper club identification. And all the trappings of outdoor subtropical living abound in Marathon - from bicycling to lounging on a hammock in the shade.

Marathon is home to 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 is the Museum of Natural History of the Florida Keys and an adjoining children's museum.

Another historical site, recently opened to the public is Pigeon Key, an tiny five-acre island nestled below the old Seven Mile Bridge. Step onto Pigeon Key and step back into history to the key that was home to the men that built Henry Flagler's Overseas Railroad.

Marathon also is home to the Dolphin Research Center and the Turtle Hospital. Both play important roles in the preservation of indigenous Keys' marine life.

Utilizing Marathon as a home base, visitors may take easy day trips to Key West and the Upper Keys. No island or attraction in the Keys is more than 60 minutes away.

And just south of Marathon, the new Seven Mile Bridge, which runs parallel to its venerable forerunner, is the longest segmental bridge in the world.

Each year, in April, Marathon hosts the annual Seven Mile Bridge Run, with 1,500 running aficionados competing in a foot race over the azure waters of the Atlantic Ocean and Gulf of Mexico.