This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

A museum dedicated to the former country.

A towering spire in the fortress of Kalemegdan honors the victorious armies of Serbia during their struggles against the Ottoman Empire.

Arguably Belgrade's only example of pure Art Deco architecture.

This striking, historic hotel has major Wes Anderson movie energy.

Backwards hour and minute hands and a timing mechanism that fluctuates with the temperature led to this clock tower's local nickname.

A tribute to an iconic act of defiance from the Croatian War of Independence involving a small car.

Twelve towering statues once destined for Pécs Cathedral, now sheltering under arches.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

A plaque bearing the names of those who dedicated themselves to protecting Budapest's Jewish population during World War II.

The metal leaves on this tree are engraved with the names of Holocaust victims.

An archway adorned with vulnerable flora and fauna.

The barrel-made lookout from Shackleton's final ship is tucked away in the crypt of one of London's oldest churches.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

A discarded movie prop that was the original monolith for "2001: A Space Odyssey."

The final resting place of a German diplomat's beloved companion.

Outside of one of Britain's most renowned social clubs, a step installed specifically for the Duke.

This coffee shop lies hidden beneath a historic church.

An unusual ode to the late Irish playwright, complete with a squiggly bust and coffin-shaped bench.

An agreement meant to honor the Duke of Buckingham led to this unusually-named passageway near Charing Cross.

This giant middle finger statue sends an unambiguous message to Italy's bankers.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

A brutalist gem towering over the heart of Milan.