Once home to an aristocratic family and a workers' organization, this intricately tiled building now houses a chain restaurant.

Gilded heaven for philatelists and architecture freaks, still in full working order despite sitting atop tremulous ground.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

Many people don't realize there’s a lot going on in—and below—the world’s tallest triumphal arch.

At a museum of everyday objects, it is the act of collecting that is really on display.

The only castle in North America to ever house European sovereigns.

The collection of intricate sculptures includes one carved from a mammoth's tusk

66,000 pieces of art, donated by one of the world's richest men.

Its incredible collections are dedicated to preserving Mexico's film history.

A museum in the former home of Marxist revolutionary Leon Trotsky.

Frida Kahlo's childhood home, now a museum of her life and works.

This mid-century mural portrays humankind's spiritual and scientific journey.

This incredible college library is a visual masterpiece of mosaic art. It also looks kind of like a giant boombox.

This art shopping center still boasts pieces of its past as a textile factory.

A beautiful example of 18th-century engineering still standing tall.

The world's first museum of its kind is packed with nostalgic relics of the past.

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

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.

Its sunny hues are believed to have inspired the town's color palette.

It would take you approximately an hour and a half to walk to the end of Mexico's largest pier.

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

The last masonry skyscraper ever built reveals a transitional moment in architectural history.

A gothic church spire sits atop this skyscraper, the tallest church in the world.