From priceless treasure found inside a lost city, to an ancient manuscript hidden behind a wall, we explore mysterious secrets lost deep inside various unseen chambers, like tunnels, caves, or even burial sites.

From clandestine nuclear weapons programs to a secret Cold War bunker hidden in the mountains, or even World War 2 technology at the bottom of the sea, we explore the unlikely people, and surprising places behind the discoveries of the most top-secret information.

From ancient religious texts buried in Egypt, to cultural relics found at sea, or even a terrifying tower of skulls hiding under the earth - these lost artifacts change what we thought we knew...

From a deadly discovery hiding under one of America's most loved national parks, to a Nazi era weapon sunk off the coast of New Jersey, or even a blood thirsty predator found in Canada...