We studied the architectural remains of two Chalcolithic (Ghassulian) cultic complexes at En-Gedi and Teleilat Ghassul Area E in order to trace aspects of the architectural planning principles and methods involved in their design and construction. Architectural Formal Analysis has brought to light hitherto unnoticed spatial relations between architectural elements that seem to have structured the ritual activity at the two sites. The discerned geometric regularities imply that specific mathematical knowledge and the same set of design principles and methods were used in the planning of both complexes. The emerging pictures of highly structured ritual and of the use of geometry in Ghassulian cultic production may be used to support suggestions regarding some sort of cultic establishment (priesthood) during the Chalcolithic Ghassulian.