I suspect we are talking about hollows/depressions in near fairways. To me one of the biggest reasons for hollows is to give the errant golfer and chance to recover, but he must control his ball flight and so I especially like the use of hollows on longish holes into or across the prevailing wind. Consequently, I would prefer fairway height grass most times, but longer grass has its place as well. However, I think it is more critical near greens to have a mix of grass heights for the hollows just as its important not to continually guard greens with sand. It isn't clever design when the same recovery shot keeps popping up all day long. Mind you, this is also dependent on a good variety of green sites. All in all, hoollows and depressions are great features, but their cousin, the mound, should not be overlooked!
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