Castles were erected in strategic locations, and natural fortifications like as hills, rocky outcrops, and rivers were used wherever practical. A castle on a hill is the ideal location. The higher a castle is located, the greater its defensive advantage. However, a fortress cannot exist without a well; otherwise, the adversary may poison your water supply. Therefore, you need clear ground around the castle for building wells. Castles were also built under popular leaders at that time. For example, Henry II of England had better defenses built in his southern territory of Aquitaine because he believed it would help protect him from invasion by Louis VII of France. In conclusion, castles could be built anywhere there was space enough for their construction and security concerns required them to be built away from population centers.