Two geological phenomena in one precarious locale: a towering stone window, and a deep blue void.

This unique building in the main square stands out among the city's typically Baroque architecture.

The fishing boats that moor in this small lagoon enter and leave through a tunnel to the sea.

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

Sofia's legislative center is continuously reinventing itself.

"Holy Wisdom" overlooks the city that became its namesake.

A vast Communist-era exhibition space in the Bulgarian capital.

Different sections of the Zemun Fortress were built in the 14th and 15th century as a response to the advance of the Ottoman Empire.

The unusual sculptures are believed to be powerful political symbols.

A Red Cross memorial museum at the site of the Niš concentration camp that operated for four eventful years during World War II.

The bizarre rocks of Đavolja Varoš are the result of natural erosion.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A pair of connected skyscrapers form this symbolic gateway.

This memorial park stands on the site of one of the largest mass executions of the Second World War.

Structure built from the skulls of vanquished foes.

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

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

This one-time health resort was used by aristocrats around the world.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

This abandoned Slovenian military barracks has become a punky-political art squat.

A whimsical bridge adorned with decorative dragons.

The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

A large statue of Pope Gregory XIII in Bologna was disguised as Saint Petronius to avoid destruction.

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.