This beautiful system of tunnels built into natural rock serves as a centuries old plumbing system.

Ancient structures used to make and preserve ice in the deserts of Persia.

A 1,500-year-old, 3-story subterranean city where ancient Persians took refuge in times of war.

This ruined fortress was the stronghold for a persecuted medieval leader and his infamous Assassins.

The palace of the King of Kings, burned by Alexander the Great.

Mirrors and glass shards cover every inch of this arrestingly beautiful mosque.

Local legend says that whoever burns down this 2,000-year-old tree will only have seven days to live.

Centuries before the modern seismograph, Armenian monks measured quakes with this tilting pillar.

This Armenian monastery was carved out of cliffs and named after the spear used to stab Jesus.

Right up until the 20th century this network of man-made caves was the biggest village in Eastern Armenia.

A geological oddity topped with a 2,000-year-old pagan temple.

Monks in the empyreal Alazani River valley have preserved their 1,000-year-old winemaking tradition.

This architecturally eclectic fortress witnessed centuries of bloody turmoil, including the massacre of its ruling clan.

Legend says these stone structures are where the doomed citizens of a vanished village sent themselves to die.

Small church on top of a huge rock column.

Underground monastery and fortress.

Rock-hewn monastery complex with hundreds of cave structures tucked away into the mountainside.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

An ancient Thracian city where fire rituals were practiced on the largest cult altar in Southeast Europe.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

A little-known park with unusual, half-ruined structures and a mystical energy.

The abandoned summer estate of the former Greek Royal Family.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.