Today, we're heading beneath the streets of St. Paul, Minnesota.

Into a place, people pass over without ever realizing what's below them.

Just a few feet under the pavement, the city gives way to something older.

The temperature drops, the air changes, sound carries different down there, like it has nowhere else to go.

In those tunnels, it stays a constant 52 degrees, no matter what's happening on the surface.

It doesn't matter if it's the middle of winter or in the heat of summer.

Down there, it never changes.

What exists beneath the city is a network of sandstone tunnels carved directly into

the bluffs along the Mississippi River.

Over the years, those spaces have been used for a lot of different things, each one leaving

something behind.

It started as a silica mind, cut into the earth for industry. Then it became a mushroom farm, quiet and methodical, rows of crops growing in the dark.

At one point it even operated as a nightclub, filled with music, light, and people who were not supposed to be there.

And for a time, it provided cover for some of the most violent criminals in American history.

Men who could disappear underground and walk back out untouched.

But for the people who have spent time in those tunnels, the story does not end with what is documented,

because there is another layer to that place, one that is not written in records

or preserved in photographs. It's tied to something known as the O'Connor Agreement,

an arrangement that turned the city into a sanctuary for criminals. And according to the legend,

it's not something that ever truly ended.

Do you believe in ghosts?

Join me on a journey through history's darkest corners, where folklore, hauntings, and

...