This modest post office sits on the site of H.H. Holmes' famous murder castle.

These abandoned grain silos and tunnels are an urban exploration dream.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

A little-known subterranean street runs under some of the best-known buildings in Chicago's River North.

Former hotel turned into haunted playground.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

Chicago's North Park Village was once the largest municipal sanatorium in the country.

Chicago's largest cemetery is full of beautiful Victorian monuments and more than a few ghost stories.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

A hollow cement depiction of time's inexorable effect on the human body.

This unauthorized stone mermaid was secretly carved out of public stone before being permanently preserved.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

An enormous park-like oasis, full of famous Chicagoans' graves.

A lush green oasis in the middle of Chicago.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The abandoned ruins of America's first private zoo are open for exploration in the Catskills.

An enormous cat made of recycled wood scraps.

This once sprawling resort now sits abandoned, filled with graffiti and vibrant colors from an era long passed.

This Central New York ghost town was once a prosperous railroad community.

The dairy farm in upstate New York where nearly half a million people gathered for three days of peace and music in 1969.

These mouldering mansion ruins remember a time when the Catskills were nothing but luxury.

This mouldering abandoned mental hospital was once a center for progressive healing.

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

A toxic ghost town sitting atop a massive coal fire.