Historically, the basic principles of crystallography were deducted from the analysis of crystal morphology.(1) German physician and mineralogist Hessel concluded, in 1830, that all crystal forms can be described by 32 different combinations of symmetry elements. Others have shown that these sets of symmetry are identical to the 32 point groups that describe the atomic symmetries. The correlation between the chirality of crystal morphologies and their crystallographic structures has been demonstrated by Pasteur,(4) Donnay, Harker, the more recent work of Lahav and Leiserowitz and others. The geometric symmetry of the external crystal habit of crystals is often related to their internal molecular symmetry. In other words, the point group symmetry of the crystal morphology is dictated by the crystal structure, i.e., the space group of the crystal. Mathematical tools for the description of crystals include space groups (= a set of symmetry elements related to the atomic disposition in the unit cell), point groups (= a set of symmetry elements that operate on an infinite three-dimensional lattice so as to leave one point unmoved) and their related forms (= a set of identical crystal facets related by the symmetry of the point group). These concepts allow one to correlate symmetries from the atom disposition to morphology, and vice versa. Point groups are obtained by removing the translational elements from the space group, and for each point group, only defined forms can exist. The crystallographic rules are well-established and classified in the International Tables for Crystallography (IUCr) and comprehensively describe the symmetry of almost the entire range of known (bio)minerals and synthetic crystals. There are only a few exceptions; quasi-crystals have forbidden symmetries at the molecular level that are inconsistent with all space groups.(13) Single crystals with a multidomain appearance are another intriguing class, having a complex, rather than polyhedron, habit. These crystals are atomically defined by space groups but defy the conventional description of point groups and forms. They have been observed primarily as rare examples in biomineralization; other examples were obtained by using calcium carbonate and templating agents. Recently, we demonstrated this phenomenon by using metal-organic frameworks (MOFs) to form single crystals with extraordinary curved and multidomain morphologies. The mechanisms involved in the formation of MOF's having unusual morphologies have yet to fully understood. In this work, we report a unique paradoxical crystallographic phenomenon: single crystals with a multidomain polyhedron morphology and concave (re-entrant) angles. According to accepted crystallographic conventions, these characteristics should not coexist: it is thought to be impossible to generate structures featuring re-entrant angles with any of the unit cell geometries. We show here that such a morphology does exist when a hexagonal unit cell has the rare space group P622.