In another thread Ian Andrew gives a lovely description of Highland Links by Stanley Thompson where Thompson designed the 11th hole as a breather hole, one that follows the previous stretch of holes which are a roller coaster ride, and one which precedes another stretch of challenging holes.
As I read it (I've not played the course), this hole in isolation might be the least inspired on the course, or at least the simplest design but nevertheless its worth to the course as a whole is more than the worth of the individual part (my interpretation and in fairness, Ian makes it sound a terrific hole). Maybe in this respect it could be said to be the cornerstone or keystone of the course.
What other holes are there that make a course work, either by accomodating a particular routing, or holes that simply add much needed balance or contrast that helps the course as a whole ?
Niall