Jamieson, Fausset and Brown on 2 Chronicles 26:9

9. Uzziah built towers in Jerusalem, &c.--whence resistance could be made, or missiles discharged against assailants. The sites of the principal of these towers were: at the corner gate (2Ch 25:23), the northwest corner of the city; at the valley gate on the west, where the Joppa gate now is; at the "turning"--a curve in the city wall on the eastern side of Zion. The town, at this point, commanded the horse gate which defended Zion and the temple hill on the southeast [Bertheau].