Charles Ellicott Commentary 1 Kings 11:7

"Then did Solomon build a high place for Chemosh the abomination of Moab, in the mount that is before Jerusalem, and for Molech the abomination of the children of Ammon." — 1 Kings 11:7 (ASV)

On the hill that is before Jerusalem.—evidently on the Mount of Olives (part of which still traditionally bears the name of the “Mount of Offence”), facing and rivaling the Temple on Mount Moriah. Tophet, the place of actual sacrifice to Molech, was in the valley of the son of Hinnom (2 Kings 23:10; Jeremiah 7:31), which was east or south-east of the city, and would lie not far from the foot of the mountain.