The Ophel is part of the Eastern Hill that sits between the City of David and the Temple Mount. The word “ophel” means “swell or rise” and refers to a higher part of the landscape. The Jebusites built their citadel there, as did David, who also added a lot more fortification to this northern part of his city.

The Ophel is mentioned in 2 Chronicles 27 and 33:

Jotham rebuilt the Upper Gate of the temple of the Lord and did extensive work on the wall at the hill of Ophel. - 2 Chronicles 27:3

Afterward he (Manasseh) rebuilt the outer wall of the City of David, west of the Gihon spring in the valley, as far as the entrance of the Fish Gate and encircling the hill of Ophel; he also made it much higher. - 2 Chronicles 33:14

This part of the city was always heavily fortified, as seen in Nehemiah 3:26, Isaiah 32:14 and Micah 4:8. Extensive building took place in this area from the days of David right up to the modern excavation of the Ophel just south of the Temple Mount.