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

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

These enormous, stern-faced statues greet visitors with lanterns, and sometimes costumes.

Walk along the medieval fortifications that have been protecting Tallinn since the 14th century.

During the Soviet era, the spire of this longstanding church was used as a radio transmission tower.

A well-worshipped shrine to the Virgin Mary nestled inside the last of Zagreb’s historic gates.

The world's oldest known salt mine.

Inspired by the Rialto Bridge in Venice, these three clustered bridges were just one part of a Slovenian architect’s grand vision.

These abundant, over-the-top monuments are so widely scattered that they define the entire compact capital cityscape, often leading to jokes about whether there are more statues than residents.

A scenic UNESCO site that doubles as a habitat for various forms of wildlife.

Decorated with a staggering 1,380 ladybugs, the installation has turned what was once a grim, forgotten nickel mine into a landmark and a statement.

The oldest museum in Russia is home to a fascinating collection of nearly two million anthropological artifacts and anatomical curiosities.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

This chapel on a cliff is renowned for its healing powers and was founded on the site of a supposed divine intervention.

The U.S. Fish Commission’s effort to mass produce carp.

This rowhouse doubles as one of the most photographed spots in the nation's capital.

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.

The "Key of Keys" for Washington, D.C. and the apocryphal landing place for the military campaign that started George Washington's career is now at the bottom of a well.

Sip creative cocktails in the former vault of the Riggs Bank.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Depending on who you ask, this controversial treehouse is either a charmingly creative child's playhouse or an illegal encroachment on public land.

Every autumn, this grove of living fossils erupts in a blaze of brilliant golden-yellow leaves and stinky fruit.

Little has changed in the way that this mill operates since the 18th-century.

This original Mason-Dixon line cairn placed in the 1760s was put in the wrong location because of the gravitational pull of the Allegheny Mountains.