A near-circular ring of mangrove keys 25nm west of Key West, possibly a meteor-impact or karst-collapse feature, unique in the…A near-circular ring of mangrove keys 25nm west of Key West, possibly a meteor-impact or karst-collapse feature, unique in the Keys, enclosing a shallow lagoon with world-class bonefish flats, nesting frigatebirds and total emptiness. The staging point on the way to the Dry Tortugas. Named for the Marqués de Cadereita. Part of the Key West National Wildlife Refuge, established in 1908 by Theodore Roosevelt to stop plume hunters wiping out wading birds. Mel Fisher's team searched these waters for years for the Atocha treasure fleet. Anchorage: Anchor inside the ring in 2-4m sand. A rare naturally sheltered offshore anchorage, but the approaches are unmarked and shoal, so daylight and good light only. Hazards: Unmarked shoals and no services 25nm from Key West. Fully self-sufficient trip; do not attempt without good light and a careful eyeball approach. Meer