The Millennial Temple is predicted to have walls over a mile in length.

The size of it wouldn't fit in the whole of Jerusalem, let alone on the Temple Mount.

Ezekiel indicates that it will be located in the section of land known as the prince's portion [Ezekiel 45:7] about twenty-five miles north of Jerusalem in a new Millennial city of the Messiah. Ezekiel 40-48.