Mammoth Cave is a world heritage site because it is the longest mapped cave in the world (possibly up to 600 miles of passageways). Often overlooked, the backcountry trail system provides about 60 miles of hiking. The 9-mile Sal Hollow Loop Trail is the lMammoth Cave is a world heritage site because it is the longest mapped cave in the world (possibly up to 600 miles of passageways). Often overlooked, the backcountry trail system provides about 60 miles of hiking. The 9-mile Sal Hollow Loop Trail is the longest trail in the park, and one of few singletrack mountain biking trails found in Kentucky's national parks. The gentle grades and sinuous trail make a fast, great ride for a beginner. The Turnhole Bend trail follows a narrow ridge to large bend in the Green River. Due to numerous prodigious springs the river here is emerald green. Later that evening, I continued southwest to my father's place in west tennessee for a halloween gala and then further southwest to his ranch to check the deer feeding plot (turnips and mixed greens) and to witness a little target practice.