A hidden three-foot-wide house separates these two regal churches.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The most visited, and possibly most controversial, museum in Germany.

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

Mountain where Jesus was first tempted by the Devil.

Week-long block party becomes a competition for the best decorated street.

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.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

A beautifully eclectic mix of architectural styles.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.