Since the earliest civilizations, humans have needed walls to protect them. From rudimentary walls around early towns and cities to vast fortresses and castles, culminating in one of the greatest engineering triumphs of all time – the Great Wall of China.

The Great Pyramid at Giza is the only survivor of the Seven Wonders of the Ancient World. Its scale is breath-taking and it is built to the mind-boggling degree of precision. How did ancient engineers achieve this feat, and what was the purpose of this monumental and mysterious structure?

In the Middle Ages, the technology of the castle evolved by leaps and bounds. Engineers constructed some of the most spectacular buildings of all time in a dramatic arms- race. At the same time, new weapons designed to attack castles came to the fore.

Building for God reached a high point in the Middle Ages when a new engineering movement emerged in Europe, changing the rules forever. It aimed to use pioneering construction methods and architecture to create a glimpse of heaven...on earth.

Temples, designed to honor the Gods, have been at the heart of cities since earliest times. Often they have been the biggest and most impressive buildings of their age. But mysterious ancient temples crop up across the ancient world. Why are so many of these monuments carefully aligned with the sun?