The Green Grotto Caves are on the north coast of Jamaica, named for the green algae covering the walls, and structurally they are nothing like an inland cave system.
They are flank margin caves: old mixing chambers formed at the edge of the fresh water lens where it meets sea water. That process leaves a distinctive shape, and here it left two well-defined levels, which appear to record two periods with different sea levels. The system is still hydrologically connected to the coastal waters beside it, and the innermost cavern holds a crystal-clear underground lake.
The list of names it has carried is a history in itself: Runaway Bay Caves, Hopewell Caves, Cave Hall Caves, Discovery Bay Caves, Dry Harbour Caves, Rum Caves, Dairy Caves.
Each name marks a use. The first known inhabitants were Arawak people, who left pottery fragments and adzes. When the British took Jamaica, the Spanish being driven out used the caves as a hideaway. Escaped slaves used them too, which is where Runaway Caves comes from. Between the world wars smugglers ran arms to Cuba through them. In the later years of the Second World War the Government of Jamaica stored barrels of rum in the entrance.
The caves are also a working habitat: nine of Jamaica's 21 bat species live here.
Beyond the public route there is a section of wild caves with relatively undisturbed ecology, which is not part of the tour and is the reason the rest of it can be visited at all.
Jamaica
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