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

What started as a tongue-in-cheek shrine is now a full-blown museum celebrating "The Hoff" and his longtime love affair with Berlin.

This gem from the industrial age helps visitors and residents alike traverse hilly Stockholm.

A unique tribute to the millions of animals who served and died for the British military.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

The curios of pharmacist and collector Henry Wellcome.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

This pump on the bad side of Victorian London betrayed a horrifying revelation about the water supply.

London's amazing modernist public square that never was.

The last four extravagant street signs of London's historic banking street.

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

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

A small museum contains one of the largest collections of ethnic and traditional headgear in the world.

This 700-year-old structure is one of the most unique architectural and historic monuments in Gdańsk.

This old and disused water tower has received a new life as an art gallery with a piano staircase.

A secluded art gallery hidden within the cellars beneath Tallinn’s medieval monastery.

A forest park outside Tallinn full of architectural and artistic curiosities.

An unfinished complex built for children from around the world sits abandoned on the Black Sea coastline.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

Mysterious standing stone formations looks like a petrified forest.

Rock carving created 1,300 years ago 75 feet off the ground.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.