The catacomb of Kay Kavus, located on the Darband highlands to the north of the modern city of Sahneh, has a southwest looking Iwan that originally included a pair of free-standing columns. The catacomb consists of two superimposed galleries: one is even with the Iwan’s floor and contains two recesses for coffins; the other lies as a cellar beneath the upper one and has a single, larger coffin recess. Our fieldwork to determine the dimensions, architectural characteristics and other extant features within the catacomb showed that the lower hallway was a later addition to the original upper one, a modification that also triggered changes in the latter. Also, our observations revealed that the upper gallery, which is the earlier part of the complex and initially involved only a single coffin recess, was perhaps constructed in the last years of Xerxes I reign (485-450 B.C.), while the lower was affixed at a later times. Examination of the remains of the beams hewn out of the rock on the Iwan’s ceiling and their virtual reconstruction by the present author proves that the now missing capitals at Sahneh catacomb typologically resembled the distinctive Achaemenian examples.