This vast, water-filled underground labyrinth can only be toured by boat.

The ancient necropolis houses the immense rock-cut tombs of four Persian kings.

Modern-day cave dwellers carve elaborate homes out of volcanic debris.

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

The vertical-axis windmills of ancient Persia have been grinding flour for 1,000 years and counting.

A sophisticated astronomical tower built by one of the greatest Persian scholars of the Islamic Golden Age.

A spectacular rainbow of stained glass makes the "Pink Mosque" one of the most beautiful in Iran.

Iran's colorful terraces are a rare geological masterpiece.

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

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

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

Putrefaction plateaus in Iran, where the dead were sent for decontamination before going to their final resting place.

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

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

Village of slate houses, built on a white marble outcrop.

A boiling wellspring flowing with natural gas burns in a continual blaze.

A bloody history is captured in this former prison turned museum.

A 605-page Quran penned in the blood of a dictator is locked away in a mosque.

A shrine on the shores of the Tigris.