This paper presents first results within investigations of geometry of fundamentally diverse spatial macrostructural systems with hexagonal type lattice. An existence of cells named pentahedra is demonstrated by topological transformations of hexagonal prismatic honeycomb and is based on a recently discovered Phi relationship within a regular hexagonal tesselation. Here has been studied a geometric symmetry of honeycomb, filling the space with no gaps and overlaps. Finally it is pointed out that abstract or skeletal analogues of pentahedral honeycomb have effective practical uses by synthesis of artificial man-made macromedium, especially like orbital large scale structural systems.