When the Norman, French and German Crusaders began to explore the existing fortifications in the Middle East, they found things they had never seen before. The Byzantine Empire had built forts that the Saracens now held. Although they were not residential castles of the type the Normans were now creating, their construction methods gave the Normans many new ideas once they had made themselves masters of these strongholds. Let’s look at one by way of example: what were Byzantine masons able to build in that period?
The Black Tower is in one of the forts facing the Bosporus Strait. Roumeli Hissar is on the European side, Anadoli Hissar on the Asian side. The Black Tower, part of Roumeli Hissar, was built around 1100. It is completely round but designed with Byzantine complexity. Its key feature was its “oubliette,” a genuine dungeon in which prisoners could be forgotten.
The Black Tower’s main door was on the ground floor, unlike the Norman keeps with their second-story doors. The ground floor, like upper floors, had a central round room. It was much smaller than the outer size of the tower, because the tower’s walls were so thick. On the first floor, and on some of the upper floors, the round room had square room extensions, probably curtained, in which private business could be handled. They got a little bit of daylight, by means of a long window shaft through the thick stone. Latrine chutes were built into the walls in a few places, and upper floors had fireplaces with simple chimneys.
One spiral stair connected all of the floors. At the sixth level above ground, there was a “secret” doorway. It led into a deep hole built into the thick wall, which extended down to the next floor level. When a prisoner was pushed into the doorway, he fell thirteen feet to the bottom of a completely dark hole. The oubliette wasn’t the only dark room, it was simply the worst. The Tower always functioned as a prison as well as a fort, so many of the lower rooms had no windows. (Note: History of Fortification from 3000 BC to 1700 AD points out that it’s not always clear what structures like this were for. The oubliette could also have been a reservoir for water storage.)
The Black Tower’s ground floor entrance could be protected from high above, because another set of shafts were built into the wall here. They allowed soldiers on the upper floor to drop boiling oil or rocks onto attackers. Machicolations, as these holes became known, were eventually built into all serious castles in Europe, but these were probably the first such that the Crusaders had ever seen.
Byzantine masonry skill was far beyond anything the Northern Europeans had dreamed of yet. Their builders did not have the skill to plan a tower with so many shafts of different sizes and angles. We can imagine that it wasn’t long until the Crusader kingdoms were hiring Byzantine masons if at all possible. Masons who traveled along to help build walls were able to learn a great deal.