These two 15th-century metal rods allowed people to check if they were swindled or not.

Op-art architecture designed for happiness.

Baroque celebration of the end of the Great Plague of Vienna.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

A stone from Africa's tallest peak is immortalized in a Potsdam palace—but is it actually the mountaintop?

One of the world's largest ancient burial mounds.

A 20th-century naval quarantine center is now a local park.

A multi-story, retro videogame time capsule in the Netherlands.

This 17th-century house has a long and colorful history.

A memorial commemorating the man whose name became synonymous with taking a picture in the Netherlands.

This small monument marks the divide between the Atlantic and Indian Oceans at the southernmost tip of Africa.

Some of the specimens on display at the Leiden University Medical Center have been helping educate physicians since the 17th century.

Lines on the pillar of Heidelberg's Karl-Theodor Bridge record the dramatic heights of past floods.

This smaller cousin of the Forbidden City has gone from ancestral sacrifice to tourist's whispers.

Where George Lemaître discovered the expanding nature of the universe.

The Lund University's former gym houses a museum focusing on the creative process of art.

A monumental toilet that is also host to rare plants.

This 19th-century zoological collection has withstood the test of time.

An installation that makes understanding the size of the universe a walk in the park.

Though they might seem like arbitrary scratches in the wall, these were once official measures of length.

The Belgian library displays burned books that were salvaged from the fires of both world wars.

Above the door of a house, a plaque claims to commemorate the future living place of the inventor of time travel.

A larger-than-life monument to the inventor of the Bunsen burner.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.