Mammoth Cave, in Kentucky, is 85 miles by rail SSW. of Louisville. The cave is about 10 miles long; but it is said to require upwards of 150 miles of travelling to explore its multitudinous avenues, chambers, grottoes, rivers, and cataracts. The main cave is only 4 miles long, but it is from 40 to 300 feet wide, and rises in height to 125 feet. Lucy's Dome is 300 feet high, the loftiest of the many vertical shafts that pierce through all the levels. Some avenues are covered with a continuous incrustation of the most beautiful crystals; stalactites and stalagmites abound. There are several lakes or rivers connected with Green River outside the cave, rising with the river, but subsiding more slowly, so that they are generally impassable for more than six months in the year. The largest is Echo River, three-fourths of a mile long, and in some places 200 feet wide. The air of the cave is pure; the temperature keeps at about 54°.
There is an elaborate work on The Mammoth Cave of Kentucky by H. C. Hovey and R. E. Call (1897); for the fauna, see works cited at CAVE; A. S. Packard, The Inhabitants of the Mammoth Cave (1872); and a memoir on 'The Cave Fauna of North America' (1888).