Ezekiel Chapter 43 Vs. 16

 The Altar

And the altar shall be twelve cubits long, twelve broad, square in the four squares thereof. Eze 43:16

And the alter... If these are the regular 18 inch cubit, the altar is (18 feet long). It will also be (18 feet broad). The lower settle could symbolize the mount of God, and the upper settle could be speaking of the hearth of God.

At any rate, this is where the sacrifice is made.

The height of the altar above the ground (10 cubits) corresponds to the altar constructed by Solomon (2Ch. 4:1).