Cities in the Sky (Full Episode) | Lost Cities with Albert Lin Compilation | National Geographic

Key Concepts

• LiDAR (Light Detection and Ranging): A remote sensing technology that uses laser pulses to create precise 3D models of the Earth's surface, capable of "stripping away" vegetation to reveal hidden archaeological structures.
• Ground Truthing: The process of verifying data collected by remote sensing (like LiDAR) through physical exploration and on-site archaeological investigation.
• Tairona Civilization: An ancient culture in Colombia’s Sierra Nevada mountains known for building complex cities on steep ridges.
• Nabateans: An ancient nomadic Arab people who transitioned to a sedentary lifestyle, eventually building the city of Petra.
• Wat’a: An archaeological site in the Peruvian Andes that predates Machu Picchu, serving as a key example of pre-Inca and Inca architectural evolution.

1. Ciudad Perdida (The Lost City), Colombia

• Context: Located in the isolated Sierra Nevada mountains, this site was built around 600 AD by the Tairona people. It housed an estimated 2,000–3,000 people at its peak, with up to 10,000 in the surrounding basin.
• Methodology: Albert Lin and archaeologist Santiago Giraldo utilized aerial LiDAR mounted on a helicopter. The scanner emitted 400,000 pulses per second to penetrate the dense jungle canopy.
• Findings: The LiDAR data revealed a complex network of terraces and pathways previously hidden by 400 years of forest growth. The team successfully identified a previously unknown, potentially new city site on a nearby ridgeline.
• Ground Truthing: The team trekked through rugged terrain to confirm the LiDAR data, discovering ancient pottery fragments and stone walls, confirming the presence of Tairona settlements.

2. Sela, Jordan: The Origins of the Nabateans

• Context: Sela (Hebrew for "rock") is a high-altitude site in the Jordanian desert. It is believed to be a precursor to the famous city of Petra.
• Key Discovery: Using drone-based LiDAR, the team identified 51 underground water-harvesting tanks.
• Significance: These tanks could store approximately 200,000 gallons of rainwater, allowing over 1,000 people to live permanently in an arid, mountainous environment. This demonstrates the Nabateans' transition from nomadic desert dwellers to a sophisticated, sedentary society.
• Quote: "They were nomads at the beginning. They were like wind... And then they, there was a shift in their consciousness. I mean they started to be attached to the land." — Mohammed Najjar

3. Wat’a, Peru: Pre-Inca Foundations

• Context: Located at 13,000 feet, Wat’a is older and higher than Machu Picchu. It is referred to as an "island in the sky."
• Methodology: The team used drone-based LiDAR at extreme altitudes to map the site. Machine learning algorithms were applied to the data to identify circular structures, which are characteristic of pre-Inca architecture.
• Findings: The scan revealed a clear distinction between older, circular pre-Inca residential structures and later, square Inca constructions.
• Synthesis: The evidence suggests that the Inca did not build in isolation; they incorporated existing sacred sites and belief systems into their own empire. The site served as a public space for community events, with the Inca later expanding upon these foundations to assert their authority.

Synthesis and Conclusion

The video illustrates a "new golden age of exploration" where 21st-century technology bridges the gap between legend and reality. By using LiDAR to "strip away" the obstacles of nature—whether dense jungle, arid desert, or high-altitude peaks—archaeologists can now visualize entire landscapes in 3D before ever setting foot on them.

The recurring theme across all three sites is the human ingenuity required to adapt to extreme environments. Whether it is the Tairona’s terracing in the jungle, the Nabateans’ water-harvesting in the desert, or the Inca’s integration of pre-existing sacred sites in the Andes, these technologies prove that ancient civilizations were far more expansive and sophisticated than previously understood. The combination of high-tech aerial scanning and traditional "boots on the ground" archaeology remains the most effective framework for uncovering the hidden history of human civilization.