The beautiful baroque library of the Hapsburg empire.

These 12th-century catacombs carved into a mountainside were a place of mysticism and Christian hermitages.

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

These expertly crafted, scientifically accurate glass sea creatures were once an international phenomenon.

The first evidence of some of the Earth's earliest life was found in this fossilized undersea grotto.

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

Tucked in the back of this amazing antique store is an important piece of medical history.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.

This preserved wilderness hides the remains of a colonial grain mill used to feed George Washington's troops.

As telephones become more essential and less stylish one historic Brooklyn building remembers the days when they were a grand celebration of communication.

This old estate is a remnant of when the Bronx was a popular summer destination for wealthy New Yorkers.

The largest known open fault in the United States is basically a giant natural refrigerator.

The lost town of Neversink, sunk by New York City.

The remains of what was once the world's steepest passenger funicular.

Collect holy water from a Bronx grotto.

The first museum in the United States dedicated entirely to posters.

This dilapidated castle-like structure overlooks the Hudson River at one of its widest points and was once home to nuns.

A millionaire's abandoned swimming pool from the gilded age of one of America's most distinguished families.

This derelict building used to house infirm Freemasons, their widows, and orphans.

The Hudson River School comes alive at this palatial estate.

This abandoned cemetery is crumbling into ruin, exposing the artifacts and bodies buried there.

Every animal in the torah taxidermied and crammed into a Brooklyn townhouse.

A town trapped in time - 1958 to be exact.

Church in Manhattan holds the bloody sock of Padre Pio, among with many other unusual relics.