The longest known cave system in the world spans hundreds of miles beneath the hills of Kentucky, and containing prehistoric artifacts and ancient human remains, experts reveal a subterranean mystery that may have changed the course of U.S. history.
纪录片由历史学家、工程师和专家共同出镜，旨在揭示那些看似超越人类想象的地下结构, 肯塔基州的猛犸洞穴系统绵延数百英里，不仅拥有壮观的喀斯特地貌，还蕴藏着史前文物和古代人类遗骸, 曾认为洞穴内的凉爽蒸汽能治愈肺结核，将猛犸洞穴设为实验疗养院。这段历史也构成了洞穴“谜团”的一部分，涉及患者与奴隶在地下共同生活的复杂故事.
