Ezekiel 42:3, 19-20

Over against the twenty cubits which were for the inner court, and over against the pavement which was for the utter court, was gallery against gallery in three stories.

He turned about to the west side, and measured five hundred reeds with the measuring reed. He measured it by the four sides: it had a wall round about, five hundred reeds long, and five hundred broad, to make a separation between the sanctuary and the profane place.