Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.

Seaside ruins of a settlement that date back to the first century B.C.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.

Medieval ruins nestled within a breathtaking swath of Spanish nature.

A spectacular walk on the flank of a gorge.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Experience what life was like in Ireland during the Viking and medieval ages.

This cemetery overlooking the Benbulben rock formation is the final resting place of one of Ireland's most beloved poets.

The oldest Roman lighthouse still in use.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

This curious, round temple is the oldest still-standing marble building in Rome.

A massive marble foot is tucked away in a small alley near the Pantheon.

This ancient market is often referred to as the oldest shopping mall in the world.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

This strange statue features a bust of the famous composer plopped atop a woman's body.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

An architectural oddity hides in plain sight on this iconic London bridge.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This sculpture marks the spot where one of the greatest Roman rulers was proclaimed emperor.

This memorial to World War II's fallen airmen shows us the movements of the stars that once guided them.