Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

This downtown Dallas art installation is always on the lookout.

A mysterious shape catches the eye in this 16th-century painting.

A harrowing sculpture commemorates the four people shot down during the workers strike of 1842.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

This unattributed sculpture in Amsterdam is hiding in plain sight.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

A floating cat sanctuary on an Amsterdam canal.

A beautifully eclectic mix of architectural styles.

Amsterdam's former hotspot for public executions and dissections.

A huge musical instrument played by the ocean.

A curious collection dedicated to human and animal anatomy and pathology.

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

Pagan monument converted to Christianity with the population.

66,000 pieces of art, donated by one of the world's richest men.

This strange building looks like a medieval fortress crashed into a 1960s Brutalist office block.

A labor of love and aviation in Nigeria.

Cliffside houses provide a spectacular view from their perch above the valley.

The second-longest pier in the U.K. stretches a whole kilometer into the Irish Sea.

Fulham F.C. imploded once everyone excised its giant, hated tribute to the King of Pop.

One of the oldest amusement rides in existence was a huge disappointment to its creator.

Locals spent years successfully fighting to save this beloved Brutalist behemoth from demolition.

Stonehenge has nothing on Castlerigg’s views.