A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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

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

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

A preserved portion of an ancient Athens barrier is displayed in a hotel basement.

This graffitied 19th-century building was a prototype of European industrial architecture.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The hallucinogenic center of the ancient world.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

Rich with fauna and flora, nature-lovers can walk across the sea at this UNESCO World Heritage spot.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

Unsurprisingly, Holland is home to one of the most magnificent flower gardens in the world.

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

Amsterdam's former hotspot for public executions and dissections.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

This cheese shop also houses a museum devoted to Dutch dairy.

Museum preserving torture methods from the past.

This museum is dedicated to the most famous Irish writers in history.

A devastating booze inferno poured through the streets, claiming several victims who drank it.

The modern birthplace of Irish freedom.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."