When Trelleborg, a mysterious Viking fortress lost underground for over a thousand years, is discovered in Denmark, archaeologists investigate its buried treasures to reveal why it was built and what caused the end of this fearsome civilization.

A mysterious city in ancient Egypt, Thebes, is the home of the Valley of the Kings, Luxor, Karnak, and other grand temples, and new discoveries reveal how they were built and if the god the pharaohs worshiped here helped them rise to power.