Jamieson, Fausset and Brown on 2 Chronicles 23:14-15

14-15. Slay her not in the house of the Lord ... and when she was come to the entering of the horse gate by the king's house, they slew her there--The high priest ordered her immediately to be taken out of the temple grounds and put to death. "And they laid hands on her; and she went by the way by the which horses came into the king's house: and there was she slain" (2Ki 11:16). "Now, we are not to suppose that horses came into [the king's house] of residence, but into the king's (horses') house or hippodrome (the gate of the king's mules) [Josephus], he had built for them on the southeast of the temple, in the immediate vicinity of the horse gate in the valley of Kedron--a valley which was at that time a kind of desecrated place by the destruction of idols and their appurtenances" (2Ki 23:2, 6, 12) [Barclay, City of the Great King].

2Ch 23:16. Jehoiada Restores the Worship of God, and Settles the King.