I just learned this fact and I can't help but share it with you!!!
In 13th-century European castles, separate fortresses were rarely built. Instead, one of the towers was significantly larger than the others and served as sleeping quarters for the lord or the king and his family.
Medieval life was full of changes and conflicts. Periods of peace were often interrupted by wars and sieges. To protect the ruler and his family, spiral staircases were built in the towers, winding clockwise. This design made it harder for attackers, as defenders could strike while using the wall as a shield, whereas attackers, especially right-handed ones, faced difficulties.
Additionally, the steps were uneven in height and length, making it easier for defenders, familiar with the layout, to move quickly. Attackers, in heavy armor and unfamiliar with the stairs, risked losing balance. This design significantly complicated sieges, particularly when climbing upward, giving defenders an advantage.
Thus, clockwise spiral staircases were not only convenient but also a crucial part of defensive strategy.