Haystacks occur in karst terrain, generally in tropical regions with high humidity. Remnants of ridges or plateaus, they represent one form of tower karst. Haystacks are in effect vestiges of an earlier, more elevated topography; they simply have not subsided as far or as fast as the surrounding landscape. Their characteristically weathered and slump-shouldered forms may resemble slightly lopsided haystacks, loaves of bread, or trafﬁc cones, and they tend to be covered by shrubs, vines, and small trees. Haystacks are common in Cuba, where they are generally called mogotes, and in northern Puerto Rico, where they are called pepino hills, and range in height from a few feet to a maximum of about 150 feet. They give a landscape an odd, arbitrary, and discontinuous look, and invite mythological speculation.