Beneath the forests and mountains of North America, ancient writers, Viking sagas, and Indigenous legends all hint at the same thing: a forbidden realm once ruled by towering “First Builders” and spirit-like giants. From Markland and the Skrælingjar to Plato’s western continent, Phoenician sea-lords, Irish monks, Cherokee cave-people, and Lakota emergence myths, asking whether a lost civilization was quietly buried under what we now call National Parks. We’ll dive into Mammoth Cave, Lovelock, Spirit Cave, Ozark bluff-dwellers, and Mississippian “dark zone” cave cults to see how miles of underground passages, sealed tombs, and redacted archaeology form a literal second landscape beneath our feet. Layered over that, we confront the modern shadows: cartel grow-sites, human-hunting precedents, Bohemian Grove–style retreats, secret bunkers, and a federal system that refuses to release basic missing persons data from these same protected zones.