From a revolutionary war era ship hiding under the streets of Manhattan, to a sprawling Roman villa unearthed in the backyard of an English home, the strange structures uncovered in this episode sometimes lead to more questions than answers.

We explore some of the most valuable treasures found in the most unlikely of ways. Like a priceless Ancient Roman mosaic hiding in a New York city apartment, or the most valuable piece of Americana tucked away in a $4 flea market find.

From priceless treasure found inside a lost city, to an ancient manuscript hidden behind a wall, 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, 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 about certain sacred beliefs.