Unrepaired walls from a 1920 anarchist bomb attack.

Possible relics of the ancient Roman city are hidden in this restaurant's façade.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

Once the tallest building in the world and the site of “the highest dinner ever held in New York” this building now holds the most expensive penthouse in the city.

Try not to get slimed in Tribeca.

A hidden "place of interment for gentlemen."

Love, knishes, and best wishes from this legendary Lower East Side bakery.

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

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

This morbid, delightful curiosity shop offers everything from animal bones to human teeth.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Once at the center of U.S. finance, the historic Trading Room was meticulously recreated piece by piece and rebuilt in the Art Institute.

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

This historic hotel invented the chocolate brownie.

A military museum and library dedicated to the citizen soldier.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

The palatial McDonald's that inspired Wesley Willis.

An abandoned church gets a second life as a massive beer hall and event space.

Huge masonic hall in Philadelphia with lavishly themed rooms.

This English-inspired Maryland garden is home to acres of opulent plant life including bushes shaped into an entire fox hunt.

The Decoy Capital of the World.

Once forgotten, this strip of sand was a rare beachside haven for Black Americans in Atlantic City.

Step inside Lucy, the world's largest "elephant."

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.