- Beautiful Key Colony Beach is located on Marathon Key in the heart of the Middle Keys. It is a scenic two hour drive down the Overseas Highway from the Miami Airport or a forty minute flight into nearby Marathon Airport. Sea Isle Condominiums are just a few minutes away. Weekly & Monthly Rentals P.O. BOX 510151 1101 WEST OCEAN DRIVE KEY COLONY BEACH, FL 33051 305-743-0173 FAX 305-743-9007 There ...www.sea-isle-kcb.com