Zechariah 2:2

"Then said I, Whither goest thou? And he said unto me, To measure Jerusalem, to see what is the breadth thereof, and what is the length thereof."

This emphasizes the purpose of the vision, the portrayal of the unlimited, glorious extent of God's city. This was not done by the announcement of any dimensions, but by a heavenly interruption that revealed the utter impossibility of measuring the city. No attempted "measuring" ever took place.

"To measure Jerusalem ..." That this is impossible of any application whatever to the physical Jerusalem is clear enough from the fact that the indicated greatness of it far surpasses anything that could have ever been true of the literal Jerusalem. This is also clear from the Messianic overtones that dominate the whole chapter.