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

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

A hot dog stand where the heads are just as hot as the dogs.

Built to house a chapter of the Knights Templar, this grandiose building is a relic of Freemasonry in Chicago a century ago.

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

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

A monument to the art of slicing people open.

Years of archaeology, just chillin' by the water cooler.

What's left of the ruins of the 1893 Columbian Exhibition, or World's Fair, also known as the White City.

All of Chicago's wood-paved streets are long gone but two alleys remain.

This historic hotel invented the chocolate brownie.

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

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

A century-old hotspot for jazz, frequented by everyone from Charlie Chaplin to Al Capone.

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

A speakeasy takes on Chicago's drinking culture.

A giant bronze coil of feces is both a tribute to doggie defecation and a reminder to pick it up.

A lush green oasis in the middle of Chicago.

An antiquated German apothecary on Chicago's North Side.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.