Ezekiel 42:3, 19-20

Facing the twenty cubits that belonged to the inner court, and facing the pavement that belonged to the outer court, was gallery against gallery in three stories.

Then he turned to the west side and measured, 500 cubits by the measuring reed. He measured it on the four sides. It had a wall around it, 500 cubits long and 500 cubits broad, to make a separation between the holy and the common.