As a residential security expert and physical security professional, I love old fortifications like these. There is a lot involved and generations of knowledge used to build them. Attack angles, lines of fire, and number of fighting positions are just the beginning.
They naturally wanted them to be both beautiful and efficient. By efficient I mean defense capability. In my line of work, the primary objective is layered defense. The more layers, the more time. No fortification was impenetrable. The better ones just gave the defenders more time.
This one is a very good example to study. They have tons of firing positions and very few blind spots. I wonder why they drained the moat though. That would be an interesting thing to discover. Perhaps the maintenance costs were too high to keep it filled in with water.
Even the way the fortifications were laid out was important. The objective was to route attackers into kill cages, open ground, or where your defenses were the strongest. The images above will give you a good example of how they were working towards that objective.
This fort was designed well, and the architects were masters of their craft!
RE: ADSactly Travels - Red Fort - The Pride of India