7. The Crusaders' Lost Fort (2006)

1179: The Crusaders build a new and supposedly impregnable fortress at a crossing on the Jordan called Jacob's Ford. Within a year of its completion, the castle, which was protected by 1500 Knights Templar, was taken in a siege lasting just five days. Dr Thomas Asbridge is trying to solve the mystery of why the stronghold fell so quickly. 1/6.

Release date: 2006-04-14