 Two caves and two former gold mines are located at the base of the andesite cap on Upper Table Rock . The caves were created by natural fractures in the cap , and the gold mines were excavated by prospectors searching for gold in the 19th century . Three are large enough to walk into , with an average width of 8 feet ( 2 m ) , while one is a small pit , dropping 30 feet ( 9 @.@ 1 m ) vertically into a pond of water . 
