I often have SurvivalBlog readers and consulting clients ask me about the "ideal" terrain for a rural survival retreat house. I must report that there is no single "best" answer because there are significant trade-offs related to terrain. Castles were situated on hilltops for centuries, for obvious reasons: Enemies had to fight uphill Defenders were able to see approaching armies from a long distance. They were also able to exploit the potential energy of stored boulders and other heavy objects. However, in the context of a modern survival retreat, a commanding position makes hilltop structures hard to miss.
The goals of privacy and advantageous fields of fire are often mutually exclusive. Likewise, a hilltop position and a spring water supply are also mutually exclusive in all but the rarest of cases.
I did some consulting for one retreat owner in the Inland Northwest who owns a small secluded side canyon that adjoins a fairly major river. From nearly all of this 120 acre parcel there is no line of sight to neighboring ranch houses. It is a landlocked parcel--you must transit through a half mile of a neighboring ranch before reaching to the highway. There is only one viable road approach to the property. With dense timber in the canyon, the access road is a long series of potential ambush sites for defense. The canyon is narrow enough that if the road were blocked--(by a D6 Caterpillar tractor and/or fallen trees, for instance)--there would be no way to get vehicles in there. Just one well-positioned listening post/observation post (LP/OP) would provide plenty of warning time under most circumstances. In my opinion, if a particular group of looters is stealthy enough to approach without being noticed by a 24 hour LP/OP and seismic intrusion detection sensors, then they would be a formidable test to any retreat's security, regardless of terrain advantages or disadvantages.
Being down in a canyon is also has an advantage for noise and light discipline. When everyone for miles has no power, and you still do, (because you planned ahead and put in a PV, wind power, and/or microhydro power system), those lights can be a "come loot me" beacon. Sitting on high ground further magnifies the effect. (Blackout blinds and other countermeasures are mentioned in my novel Patriots.) Further, a retreat on commanding high ground is a lot more likely to be spotted by looters making a "sweep" through an area than one that is nestled down in a tree-filled canyon. The major drawback--as is often mentioned--is the inherent disadvantage of being on low ground versus high ground. In general, I agree that it is best to opt for a piece of high ground with open fields of fire. In this particular instance, however, I supported the decision on where to build the house. The owner realizes that his decision will necessitate posting more security (including a seismic intrusion detection system) to allow more warning time of anyone approaching on foot. The worst case would be a large group approaching on foot by an unlikely route (i.e. not on the road), at night. Under circumstances like that, it would take a very hard home, indeed, to keep the bad guys from coming in the door. OBTW, I'll have more on the "Harder Homes and Gardens" aspects of retreat architecture in an upcoming post.