[L. cavus, hollow.] A hollow place underground. Among the most interesting caves are the Mammoth Cave of Kentucky ; Fingal's Cave, a basaltic cave in Staffa, Scotland; the Adelsburg caves, in Carniola; and the Luray cave, in Virginia. Many caves contain splendid stalactites and stalagmites. Mammoth Cave has been penetrated for 10 miles, and contains a river and many splendid apartments. The greatest caves occur in limestone strata. Primitive man seems to have dwelt in caves, and bones and implements left by him have been found there.