Young Brunette Girl Outside On A Green Hill

In northern Europe, many ancient monuments are sited in heaps. Some of these are defensive structures (such as the hill-forts of the Iron Age), but others appear to have hardly any significance. In Britain, many churches at the tops of hills are thought to have been built on the sites of earlier pagan holy places. The National Cathedral in Washington, DC has followed this tradition and was built on the highest hill in that city.
Military significance
Hills provide a major advantage to an army, giving them an elevated firing position and forcing an opposing army to charge uphill to attack them. They may also conceal forces behind them, allowing a force to lay in wait on the crest of a hill, using that crest for cover, and firing on unsuspecting attackers as they broach the hilltop.