The team arrives at Guédelon, in the Burgundy region of France, to join the world's biggest archaeological experiment - a 25 year project to build a medieval castle from scratch, using only the tools and materials available in the 13th century.

A look at the ingenious features medieval castle-builders came up with to withstand attack from an ever more formidable array of siege engines.

The surprisingly colourful world of medieval interior design. The castles that we see today are in fact scarred by centuries of decay. Most of their original roofs, carpentry and interior finishes have long since disappeared, but in their heyday they were lavishly decorated.

The team delve deeper into the secrets of the skilled communities who built medieval castles. The stonemasons working on the castle walls are dependent on blacksmiths, whose metalwork was magical to the medieval mind-set.

A look at the castle's place in the wider medieval world. 13th century Europe was a busy, developing, connected place, where work, trade, pilgrimages and Crusades gave people the opportunity to travel across the continent and beyond.