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

This conical hill was built as a testing ground for an engineer known as the Glider King.

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

An eerie, derelict amusement park in Berlin.

A collection of abandoned typographic signs from Berlin and beyond.

Residents of Berlin take their coffee and cake in one of the city’s most restful spaces: a cemetery.

Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

These former Nazi anti-aircraft towers offer a singular view of the north of Berlin in the summer, and a sanctuary for bats in winter.

Blitzkrieg bop your way through Berlin's Ramones Museum.

Art and a pun, all in one.

From Iggy Pop to David Bowie to Nick Cave, this regal music studio has served some of the all time greats.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Berlin's oldest surviving academic architecture hosted decades of animal dissections.

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

The last remnants of a massive medieval wall that once encompassed the city of Berlin.

The most visited, and possibly most controversial, museum in Germany.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

The topiary maze at the Habsburg hunting lodge.

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

Apartment complexes built into huge repurposed natural gas tanks.

A spherical "micro-nation" in the heart of Vienna.

Op-art architecture designed for happiness.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.