Boats must transform into railroad cars to navigate this Polish canal.

A haunting deserted hotel is a favorite with artists and photographers.

Polish luminaries and masterful folk art find sanctuary in this unique cemetery.

An abandoned Nazi explosives plant founded by the inventor of dynamite is now an underground museum.

An eerie, derelict amusement park in Berlin.

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

A tiny replica of the iconic London landmark hides on the side of the steel structure.

A wonderfully eclectic Victorian aquarium lies in the basement of the Horniman Museum.

A network of concealed passageways lies within a busy London Underground station.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

This South London cemetery holds the remains of more than 15,000 people.

The sign at the garden gate reads: "These Plants Can Kill."

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

These fantastically named natural pools look like something out of a Scottish myth.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

Over 1,000 pieces of one of the most niche art objects imaginable: the glass paperweight.

In the center of Wrocław's old meat market stands a somber tribute to the city's livestock.

The giant statue and its model solar system honor the native Pole who declared that the Earth revolves around the Sun.

This biographical museum honors the groundbreaking scientist at her birthplace in Warsaw.

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

A collection of old neon signs from all over Poland line a secluded courtyard.

Memorial to the lost dead of Gdansk, whose resting places were destroyed during World War II.