A preserved oak tree about 3,500 years old found in Riga, Latvia.

A pair of mutilated bronze octopuses slump at the base of the monument honoring California's admission to the U.S.

Adolph Sutro's little-known, geographically inaccurate, deprecated monument.

Go inside a revolutionary, cage-less zoo where 70 species of monkeys roam free alongside their human visitors.

A beautiful maze marks where three countries meet.

Wooden pathways run through this rocky landscape, which legend says was created when a dwarven king pulled down his own castle to stop raiding giants.

This mine is home to the largest man-made hole in Europe.

Take a walk in a recreation of ancient Rome.

These tenacious 14th-century towers defied demolition and are now a fairytale vacation rental.

This futuristic German television spire is actually the world's largest digital clock.

The Bauhaus-style former industrial complex is considered the world's most beautiful coal mine.

This monolithic slab of art metal crowns a German slag heap.

The monumental home of Prussia’s eccentric "Cannon King."

This massive steel pyramid can be entered by a set of jagged steps that let visitors stand in its heart.

No need to strap in for a "ride" on this walkable roller coaster.

An industrial relic is now one of Europe's most staggering art spaces.

The world's biggest pet store.

This former steel and coal plant is now a neon-lit industrial fantasia.