King David takes the stronghold of Zion
After David was anointed king over all Israel, King David and his men went to Jerusalem against the Jebusite inhabitants of the land who said to David, "You will not come in here, but the blind and the lame will ward you off"--thinking, "David cannot come in here." David said, "Whoever would strike the Jebusites, let him get up the water shaft to attack 'the lame and the blind,' who are hated by David's soul," and defeated them. Therefore it is said, "The blind and the lame shall not come into the house." David lived in the stronghold and called it the city of David. And David built the city all around from the Millo inward. And David became greater and greater for the LORD, the God of hosts, was with him. (2 Samuel 5:1-10)
An extensive network of water tunnels have been excavated around the spring of Gihon, one of which was probably the water shaft through which David's men entered the city, led by Joab. This water shaft is often identified with Warren's Shaft directly over the water channel near the spring. (The ESV Study BibleTM, English Standard Version (ESV) by Crossway Bibles, 2007. Page 549)