North of Elliott Key are several small transitional keys, composed of sand built up around small areas of exposed ancient reef.

Fossilized coral, the remains of ancient reefs, can be found among the rocks around the flanks of the mountains.

Donald G. Mikulic has called them "a textbook example of ancient reefs."

This great book takes us to that ancient reef blocking us from the summit and then whirls and looks straight into the heart of the fire.

To the west of Key West the ancient reef is covered by recent calcareous sand.

On land, this ancient reef produces oil and gas, but is buried by thousands of feet of sediment; here it is exposed.

Some ancient reefs are used to make restorative oyster reefs in nearby sites.

Once upon an ancient reef.

Recently base rock that is mined from inland ancient reefs has become a popular way to keep the aquarium trade going sustainably.

It was the first ancient reef described in North America, and among the first described in the world.