An abandoned Byzantine fortress and notorious prison.

These ruins in Volvi were once at the intersection of the Eastern and Western Worlds.

An ancient octagonal weather station named for the eight Greek gods of wind.

According to myth, Zeus himself was hidden in this cave to escape being eaten by his dad.

Giant marble phalluses on the sacred island of antiquity.

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

The hallucinogenic center of the ancient world.

Monasteries on rock pillars, once accessible only by frayed ropes.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

The history and future of cannabis.

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

Museum preserving torture methods from the past.

This now abandoned restaurant provides some of the most amazing views of Lisboa.

This small chapel is built of human bones and decorated with a golden skeleton.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

The last fully functional fortress of Germany's World War II Atlantikwall.

Norway's oldest cathedral still in use.

Across the Pacific in a raft, a museum dedicated to Thor Heyerdahl's now legendary expedition.

Stay overnight in the world's most sleekly designed rabbit hole, free of charge.

Monuments don't get much more metal than these three giant viking swords planted in a Nordic hill.

An intricately carved Viking church overlooks a glistening fjord.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

Walk 2,300 feet above the ground on the "Troll's Tongue."

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.