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

A small cell adjacent to this church was once the bedroom for a renowned saint.

An ancient knight and a symbol of the city's freedom.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

These roaring primates were considered a divine creature in the cosmology of the Maya.

Deep in the Guatemalan jungle stands an ancient pyramid that once marked the reign of a king.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

Three sinkholes filled with warm, crystal-clear water reached by a horse-driven cart on an old train track through the jungle.

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

After becoming locally extinct, this esteemed avian now flies free in the forests around the ancient ruins.

Three small rooms in the jungle house the most elaborate and intact murals of the Mayan world.

The ruins of an ancient Mayan city, beautifully preserved and only accessible by boat.

This lovely, if imposing, piece of Canadian gothic is possibly the most photographed hotel in the world.

Claude Monet was baptized in this lavishly ornate Paris church.

France's national museum of scientific and industrial instruments.

The oldest stone house in Paris was built by its most famous alchemist.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This 18th-century sundial was designed to calculate the date of Easter each year.