Orthanc

Orthanc was a tower made of 4 columns joined together. Each one of these ended in a sharp peak that sort of made it look like a crown. The total height was 500 feet. A high stair case led to the entrance. Above that was a small window and platform. The stone was a black color and glistened as if always wet. The top platform was highly polished to the point it appears quite slick. The tower was so high that the top was a good vantage point to conduct astronomy. The tower itself is centered in a low laying basin surrounded by a form of wall.   Access to the tower was controlled by what was described as a great wall of stone called the Ring of Isengard. In the books, it is a literal ring of rock while in the movies it was a standard stone wall. This ring was a mile across. In the books, it was estimated the rim wall as about 100 feet tall. It had a gate leading to a tunnel, with iron doors at the far end. Now, there are some hints that the Ring of Isengard is made of the same stone as the tower, but this is unlikely. The ents were apparently able to totally tear down the defensive walls, but the Orthanc itself received a few minor scratches and chips. So whether through construction material or techniques, there was something fundamentally different between the wall and tower.   It is suggested that Orthanc was a sort of naturally occurring pillar with easier to quarry material on the outside. This outer layer was removed and used to reinforce the outer ring, leaving the practically invincible core to form the main tower we know. In both, the back side was the end of the Misty Mountains and the outer ring was much easier to breach than the tower itself. Directly to the south was the main gatehouse. In the movie, this was a normal gate. For the books it was a tunnel dug into the rock wall with iron gates at each end and a guardroom in the middle.   Given the nature of the book version, there was little to no standard defensive features such as machicolations. But the guardroom shows it was one of the best gatehouses I have seen in Middle Earth outside the Dwarven Kingdoms. There were two towers at the front in addition to the gates at either end of the tunnel. The guardroom also had a staircase that led to the top. This means likely the addition of murder holes along the top. The only thing that could have possibly made this better would have been a portcullis at either or both ends and arrow slits on either side to allow for cross fire. But still, this is a pretty solid gate.   Speaking of gates though – the Orthanc’s entrance was brilliant. It is located 27 steps (33 in the movies) up and had a balcony above it (200 foot elevation) to allow for downward fire on those approaching it. This is the closest I have seen to machicolations. This entrance into a tower made of impenetrable rock means there is practically no shot of getting in through direct assault. Consistent with the principles of medieval design, there were no ground level windows. Trickery, deception and sieges are the only options.