Underneath the city that invented pilsners are a series of historic tunnels that have been storing beer for centuries.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

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

The "Prussian Versailles" that is as glorious today as when it was built.

An eerie, derelict amusement park in Berlin.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The world's largest bicycle shelter can hold more than 12,500 two-wheelers.

The cutest way to stay safe in traffic.

Atop this former dutch railway office sits an interstellar work of art.

A historic observatory now an astronomy museum beautifully situated at the moat of the Middle Age city centre.

'The Letters of Utrecht' lays out a ribbon of poetry one letter at a time, with no final verse in sight.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

This historic black and white monastery is one of Bulgaria's architectural jewels.

An homage to the medieval rulers of Bulgaria.

The site of many battles and tragedies, including the 40 maidens who leapt into the sea.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

An abandoned saucer-shaped monument in the Bulgarian mountains.

The elliptical citadel resisted the advance of the mighty Ottomans several times, thanks to the military prowess of the "Dragon of Albania."

One of the best examples of a Byzantine period monument in Albania.

The largest Roman amphitheater in the Balkans once held over 20,000 people, but managed to lay hidden for hundreds of years.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

Decorated with a staggering 1,380 ladybugs, the installation has turned what was once a grim, forgotten nickel mine into a landmark and a statement.