Hezekiah dammed up the source of the waters of the Upper Gihon and directed them down to the west side of the City of David. ¹  Hezekiah succeeded in all that he did.

After this Manasseh ¹  built up the outer wall of the City of David ²  on the west side of the Gihon in the valley to the entrance of the Fish Gate and all around the terrace; he made it much higher. He placed army officers in all the fortified cities in Judah.