A marvel of Byzantine engineering under the streets of Istanbul.

This bird-loving brewery is situated in an old municipal bathhouse, nestled beside a 300-year-old windmill.

Each time a baby is born in Ghent, these streetlights flash in silent celebration.

Brussels' favorite peeing boy has a sister.

A little sculpture with a large wardrobe.

Climb inside an iron crystal magnified 165 billion times its normal size.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

A two thousand year old brothel uncovered in Northern Greece.

These ruins in Volvi were once at the intersection of the Eastern and Western Worlds.

Stockholm's deepest subway station is also a stunning ecological wonder.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Whitewashed mosque contains the world's largest carpet.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."

Neo-cave art on the macro scale.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.

A Cuban artist reclaimed his impoverished neighborhood as a dreamy folk art kingdom.

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

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

A lush oasis full of vibrant plants and striking geometric displays.

These small, triangular, colorful houses are a staple of Madeira Island.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.