Florida Keys are a group of small islands or reefs that stretch in a curved line about 150 miles (241 kilometers) long from Biscayne Bay at Miami southwest into the Gulf of Mexico. The word keys comes from the Spanish word cayos, which means small islands. The Florida Keys are remarkable examples of coral formation. The islands attract a large tourist trade. Leading tourist activities include boating, scuba diving, and sport fishing. Commercial fishing also is important to the area’s economy. Key West, farthest from the mainland, has the most important harbor. It is joined to the mainland by U.S. Route 1, an overseas highway 128 miles (206 kilometers) long.