Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

This hydrochronometer was invented by a Dominican monk and is a prime feature in this garden.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

The buildings around this DePaul University statue create an echo chamber for those standing in the center of the circle.

The site of a fallen tree that protected Americans from British forces during the American Revolution.

19th century cemetery hidden in Brooklyn's Prospect Park.

A tree that grows parallel to the ground was declared Brooklyn's "crowning curio" by the poet who saved it.

Famous for its bio-luminescent inhabitants, known as "dismalites."

You'll need cowboy boots to trek to this old-fashioned saloon nestled in a giant natural cave.

Underneath this water pump, Annie Sullivan helped Keller speak her first words.

A discreet little stairway on St. Nicholas Avenue leads to a quaint and unexpected cobblestone street of 19th century wooden rowhouses.

Located on the campus of Emory University, this museum is filled with objects from the Americas to ancient Greece.

The first integrated firehouse in Atlanta houses a museum on the history of desegregation in the city's fire department.

This secluded ruin was once a home for exotic plants.

Named the fifth most beautiful building in America in 1885, this former courthouse boasts the best view in the Village.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

New York's oldest magic store.

Walk into the 19th century without leaving Brooklyn.

The haunting ruins of a once-holy church now stand as a forgotten relic of Montreal’s past.

Every year, the colorful murals of Montreal get a complete makeover.

A fragment of one of history’s most famous walls stands as a reminder of unity in a culturally divided city.