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, 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 about certain sacred beliefs.

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, you never know where a killer find is hiding or who may stumble upon it.

The biggest and scariest beasts are actually a lot closer to us than we think. From a mythical monster that turns out to be real, to one of the deadliest prehistoric animals on the planet these startling discoveries shock and terrify the world.

From a Chinese curse that turns out to be real, to mysterious island in Central Asia with enough pathogens to kill the entire global population several times over...we uncover some of the world's most dangerous and deadly accidental discoveries.