Hamburgers are intensely proud of their tunnel beneath the river.

Designed to allow funerals to proceed over the River Dulnain.

Looking strangely like Rome's Colosseum, this unfinished tower has dominated the skyline for over 100 years.

After 800 years, Europe's oldest elm tree has met its end.

Started as a kitchen garden, now the second largest botanical garden in the world.

Northern Ireland's Brobdingnagian stepping stones.

This endearingly discomfited urinating statue commemorates the sneaky pees had by us all.

A steam powered train that runs on city streets.

Twisted trees shaped by coastal winds make this woodland look like something from a spooky story.

The sweet story of how American cargo planes became known as "Candy Bombers" during the Berlin Blockade.

The world's only silo that was topped by two revolving restaurants has unfortunately been demolished.

Fantastic views and thousands of love locks.

This unique exhibit "Dialogue in the Dark" reverses roles as the visionless become guides and the sighted become ‘blind.’

The entrance to this Frankfurt subway station looks like an old tram car crashed into the concrete sidewalk.

From Nazi chemicals to the CIA, this architectural marvel has played a fascinating role in German history.

Revitalization efforts converted a former U.S. military heliport into a sprawling urban park.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

This picturesque medieval monastery guards a small trove of historic treasures.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

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

A restaurant and observation deck built in a unique broadcasting antenna.

A traditional U-Bahn station in Berlin gets a string of rather untraditional benches.

A 12th-century fortress containing some of Berlin's oldest buildings.