Apartment complexes built into huge repurposed natural gas tanks.

For many people the Hungarian Parliament building is a must-see stop on any visit to the capital but there is an equally stunning replica hidden in a basement.

A controversial “crumpet”-shaped museum tries its best to blend in with surrounding parkland.

A museum in the childhood house of a medical pioneer.

A gigantic statue of a Russian soldier watches over the ancient city of Plovdiv, a prominent reminder of the Soviet period in Bulgaria.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

"Unity, Creativity, Beauty."

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

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

An abandoned saucer-shaped monument in the Bulgarian mountains.

Sofia's legislative center is continuously reinventing itself.

An interactive museum-like experience takes visitors back to 1980s Communist Bulgaria.

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

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

A striking symbol of the Bulgarian capital.

A collection of art from Bulgaria's time as a communist state.

A fountain standing as a testament to a doomed alliance.

Ancient serpentine sacrifice holder that has stood the test of time.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

The most metal church of all time was built in record time because of an international, pious pissing contest.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.