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

The largest statue of this convex, homogeneous object with just one stable and one unstable equilibrium point.

A cemetery for Slovenian notables also serves as a popular recreation space.

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

This 135-year-old weather station studied the effects of the climate on human health.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

Where the lovelorn find a home for their sentimental keepsakes.

One of Belgrade's most beloved animals.

This virtually windowless mass of smooth concrete is the only Catholic church in the city.

This mansion oasis contains gardens, sculptures, and fountains just off the busy Plaça Kennedy in Sant Gervasi.

This set of concrete chambers resonates according to different notes of octaves.

With over 10,000 lights, this engineering marvel lights up the city after dark.

A grand Yugoslav memorial to the group of partisans who fought and died resisting western Serbia’s Nazi occupation.

This enormous steel tube is the biggest speaking horn in the world.

An iconic Soviet statue of working-class people.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

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

The social hall of this former factory is a Communist-era time capsule.

A decaying, yet still functioning, work of communist architecture.

An homage to the medieval rulers of Bulgaria.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

The European towns of Brașov and Râșnov each have proud signs reminiscent of the Hollywood sign.