There's so much to do year-round on Key Biscayne and the attached Virginia Key that you won't even finish crossing Rickenbacker Causeway, which tethers the islands to Miami, before you find fun.  Pull your car or bicycle over at Hobe Beach for bridge fishing, swimming, jet skiing, kayaking, windsurfing, sailboarding and kitesailing (rentals available) before crossing the bridge over Biscayne Bay, which affords postcard views of the islands and the famous Miami skyline before depositing you on Virginia Key. 

Here you'll begin to find waterfront restaurants for every budget, such as the legendary Rusty Pelican and the number one-rated restaurant on the islands, Rickenbacker Fish Company, where myriad delicacies may be had.  Nearby is the entrance to historic Virginia Key Beach Park and Jimbo's, a local haunt established in 1954, which has been featured in movies and is famous for its smoked fish, cold beer and bocce court.  Just across the boulevard is the Miami Seaquarium, with its fantastic oceanarium and live shows.

The Rickenbacker gives way to Crandon Boulevard when you cross Bear Cut onto Key Biscayne proper, a two-mile-wide, five-mile-long barrier island.  Crandon Beach Park is next, where you'll swim, add to your seabean collection while beachcombing, find sea turtle nests and snorkel the fossil reef which becomes exposed at low tide and is accessible from the shore and some hiking trails that follow the wild southern shoreline of Bear Cut (all of which are part of the Key Biscayne Heritage Trail).  Crandon also features an excellent golf course and the Tennis Center that hosts the Miami Masters Sony Ericsson Open in late March.

Past the quaintly bricked downtown intersections of the Village of Key Biscayne is the southernmost destination of your adventure, Bill Baggs Cape Florida State Park , home to the oldest building in south Florida—the Cape Florida Lighthouse, built in 1825.  This park is practically within casting distance of Stiltsville on the northernmost edge of Biscayne National Park and offers many opportunities for exploring this unique ecosystem: fishing, snorkeling, swimming, kayaking, canoeing, picnicking, youth camping and hiking and biking trails that feature an astonishing array of plants and wildlife.  When you're stomach starts to rumble due to all the calories you've burned, be sure to check out the Lighthouse Cafe by the beach or the Boater's Grill in No Name Harbor (the latter also accessible by boat).  I can tell you from experience that the Grill's jumbo whole grilled snapper or grouper will feed the whole family and the homemade sangria can't be beat; they'll even cook your own catch.

So whether you're with family, friends or going solo on foot, bike, by car or by boat-if you seek fun, salt and sun you'll always find plenty of attractions, accommodations and fine fare on Key Biscayne.