Where commuters walk through remnants of an ancient Greek necropolis.

The hallucinogenic center of the ancient world.

This legendary city has been a tourist attraction for centuries.

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

The most loyal of little dogs, or a Victorian era publicity stunt?

360° views of the city plus five floors of optical illusions and hands-on science.

A 200-year-old collection of oddities and medical paraphernalia.

The world's oldest surviving music hall was also once a freakshow.

Displaced highlanders would take shelter from the wet Scottish climate under the large walled bridge at Glasgow Central Station.

This stately monument has been wearing a traffic cone hat for decades much to the delight of the locals.

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.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

Once the home of a hermetic monk, this cave now houses a small church.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.