The oldest surviving botanic garden in the United States.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A layered tribute to the work of mosaicist Isaiah Zagar.

A Prada store in the West Texas desert that is never open for business.

This is probably not the Target you're looking for.

This is one really big nut.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Occupied for six centuries by Franciscan Order nuns, this monastery is an amazing ode to Catalán Gothic architecture.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This colorful statue welcomes visitors to a Barcelona park.

An early 20th-century bullring converted into a modern shopping center.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

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

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

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

A beautiful geyser under environmental threat.

The first declared National Monument in the United States.