During World War II, a number of persistent mysteries were born including unexplained stories about everything from lost gold, to secret societies and highly advanced technology.
There are many puzzling artifacts from around the world that challenge everything known about the technological capabilities of distant ancestors; some ancient objects are so mysterious they've spawned endless debate and theories.
There are many bizarre tales involving U.S. presidents that defy explanation and are still shrouded in mystery.
During the Middle Ages, the Vikings were infamous for being a bloodthirsty band of seafaring warriors; historians are learning surprising new things about this Norse society.
Scattered across the globe lie mysterious ruins that are buried in sand-swept deserts, perched atop towering mountains, and shrouded in the heart of dense jungles. These age-old structures stand as silent sentinels from the past, their true history seemingly erased by time. Can modern archaeology unravel the enigma of how-and why-these wonders were built?
A look at whether time travel has already occurred, on purpose or by accident, and scientists who believe it is theoretically possible.
Humanity has launched satellites into outer space and submarines to the ocean floor, but the ground below Earth's surface remains shrouded in mystery. Are there profound secrets buried beneath layers of rock, or hidden in vast caves? Can the subterranean world below shed light on humanity's past, or even its future?