The legendary metropolis of Xanadu (Kublai Khan's capital of the Mongol Empire in the 13th century) and its fabled existence have mystified experts for centuries; now, archaeologists use cutting-edge aerial imaging to investigate new discoveries and reveal the truth behind this mythical lost city.

The coliseums of Rome were brutal theaters of spectacle and death that helped control the sprawling Roman empire; now, archaeologists uncover the engineering secrets behind these more than 230 majestic structures to reveal the truth behind the ancient Roman world. 

Behind the presidential faces of Mount Rushmore lies concealed secrets and the Statue of Liberty contains a dark, enigmatic history; experts use the latest science and technology to investigate and reveal undiscovered mysteries of American monuments. This is a mashup of S03E04 "Statue of Liberty: The New Secrets" and S06E04 "Mount Rushmore: The Hidden Secrets."

On the Tigris River, the ancient city of Samarra contains a series of medieval structures that hold secrets to one of the world's greatest empires, the Abbasid Caliphate; now, archaeologists use pioneering technology to investigate its astonishing rise to power and reveal its monumental downfall. 

The clifftop ruins of Tintagel Castle in Cornwall, England are shrouded in a tumultuous history and believed to be the birthplace of King Arthur; experts use cutting-edge tech to unlock the secrets of this ancient structure and reveal the truth behind a legendary ruler. 

The ancient city of Abydos contains some of the oldest Egyptian tombs and a buried temple linked to the Cult of Osiris, a mysterious death cult; now, archaeologists use cutting-edge drone imaging to investigate long-hidden secrets behind the first pharaohs.

A colossal stone temple on Philae, a remote Egyptian island in the Nile River, mysteriously bears the names of the most famous leaders of the ancient world; now, experts use cutting-edge tech to investigate why pharaohs and emperors all built monuments at this enigmatic site.

The ancient Sumerian city of Nippur is one of the richest archaeological sites on Earth, but decades of conflict in Iraq have prevented its exploration; now, experts gain rare access to finally uncover the mysteries behind the most sacred city of Mesopotamia.

The vast necropolis of the Valley of the Queens and the calamitous burial of King Tutankhamun contain lingering, ancient mysteries; experts using cutting-edge forensic archaeology to reveal enigmatic secrets behind Egypt's greatest pharaohs. This is a mashup of S09E02 "Valley Of Egypt's Queens" and S02E01 "Tut's Buried Secrets."

The downfall of the powerful Maya city of Palenque in southern Mexico continues to mystify archaeologists today; now, investigators gain rare access to explore lost tombs to reveal the truth behind this legendary city and the mystery behind its enigmatic queens. 

The sprawling capital of Persepolis and the site of the epic battle of Sparta at Thermopylae hold new discoveries waiting to be revealed; experts using cutting-edge forensic archaeology to reveal secrets behind these lost cities of ancient Persia. This is a mashup of S09E01 "Lost City Of Persia" (Persepolis) and S05E06 "Finding Sparta's 300" (Thermopylae).

The decapitated statues of Mount Nemrut in southeastern Turkey and their eventual destruction have mystified experts for centuries; now, archaeologists decode cryptic inscriptions and use innovative geophysical analysis to reveal the mystery behind this ancient megastructure. 

The Valley of the Queens is a vast necropolis near the Valley of the Kings concealing some of Egypt's most miraculous tombs and powerful women; now, investigators use cutting-edge tech to explore lost tunnels and uncover the enigmatic secrets behind these ancient pharaohs.

The sprawling city of Persepolis was the capital of the Persian Empire, the first imperial civilization that conquered most of the known ancient world; now, experts use advanced forensic archaeology to reveal the secrets behind Persia's mysterious and dominating metropolis.