Castles are usually situated on sites of stategic superiority, example of top of a hill - can see enemy advancing sooner, and it harder to atteck it after coming up a hill slow, and you can hit them...
Here's Why.
The NON MYTH version is that the Greek soldier and leader of the Greek army, Ulysses(Ulysses=Latin Version Odysseus=Greek Version, Same person) had thought of the idea to build the Trojan...