The dark blue Straits of Florida (the north-flowing Gulf Stream) with water depths exceeding 1000 feet (305 meters) contrast with the lighter blues of Biscayne Bay where water depths of 6 to 10 feet (2 to 3 meters) are common. At this scale few features of Miami are discernible—the runway and apron of Homestead Air Force Base south of city and large rectangular water-filled pits created by the excavation of limestone (bottom center)