It is a pyramidal roof on towers of square plan. Each of the four sides of the roof is rhomboid in form, with the long diagonal running from the apex of roof to one of the corners of the supporting tower. Each side of the tower is topped with an even triangular gable from the peak of which runs a ridge to the apex of the roof. Thus, the corners of the pyramidical roof do not correspond with the corners of the tower but with the peaks of the gables.
An early if not the first example of such spires can be found on the four tall towers of the Cathedral of Speyer. Rhenish helm spires are mainly found in the historical Rhineland but there are a few churches in other areas with such spires.[citation needed]
