the mystery of the central stone slab in the tripylon gate of persepolis

it has been proposed that some structures at persepolis served as calendarical or astronomical mechanisms. despite a general lack of evidence of such functionality at the site, a stone slab in the central palace (the tripylon gate) has been claimed as evidence supporting this theory. the chiseled signs on this slab have been interpreted as symbols indicating the precise time of the spring equinox (march 21) marking the beginning of the new year. the suggestion that the central palace served as an ancient observatory, however, requires a closer inspection. to properly interpret the intended function of this stone and its mysterious signs, it must be studied in the context of archaeological and architectural investigations.