Albert Barnes Commentary 1 Kings 9:24

"But Pharaoh`s daughter came up out of the city of David unto her house which [Solomon] had built for her: then did he build Millo." — 1 Kings 9:24 (ASV)

See the reference in the margin. Solomon was not satisfied that Pharaoh’s daughter should remain in the palace of David, which was on Mount Zion, in the immediate vicinity of the temple, because he regarded the whole area near the temple as having been made holy by the presence of the ark of God. His own palace was on the other (western) hill, probably directly opposite the temple, with the Tyropoeon Valley running between them.