The syntheses and X-ray structures of very Large polycyclic aromatic compounds containing clefts defined by polyphenylaryl groups are described. The C-2-symmetric "albatrossenes" 1,3-bis(heptaphenyl-2-naphthyl)benzene (7a) and 1,3-bis(heptaphenyl-1-naphthyl)benzene (12a), as well as brominated derivatives, were synthesized by the addition of tetraphenylbenzyne to the appropriate polyphenyl biscyclopentadienones. The 2-naphthyl isomers have wide, shallow clefts, and the 1-naphthyl isomers have deep, narrow clefts which were observed to change size dramatically in different crystal environments. In a similar way, 1,3,5-tris(pentaphenylphenyl)benzene (19), a D-3-symmetric molecular propeller with a diameter of 21 Angstrom, and 1,3,5-tris(heptaphenyl-2-naphthyl)benzene (22) were prepared by the addition of diphenylacetylene and tetraphenylbenzyne, respectively, to a triscyclopentadienone.