Located just south of the Temple Mount, the City of David is the oldest part of Jerusalem; its original buildings predated King David’s conquest of the city, described in the book of Samuel, by hundreds of years. The area has yielded countless archaeological discoveries, including most recently the remains of a moat separating the city from the Temple Mount, which dates at least to the 10th century BCE (the putative era of David and Solomon), and possibly as far back as the beginning of the second millennium BCE. Nathan Steinmeyer writes:
The moat would have provided a natural defense against enemies attacking Jerusalem from the north. Notably, the moat’s southern scarp is cut at a vertical angle while its northern scarp was made into a series of rock terraces. Such a defensive structure would have been very important, as the southern ridge (the City of David) sits at a slightly lower elevation than the area of the Temple Mount. . . . It remains unclear, however, where exactly ancient Jerusalem was located and, as such, whether the moat had a defensive function or served some other purpose.
It seems more apparent, however, that by the 9th century BCE, the moat had come to serve as a physical barrier . . . to separate Jerusalem’s acropolis from its lower city. This barrier appears to have remained in place until the late 2nd century BCE, when it was finally filled in and covered over to allow for new construction.
Read more on Bible History Daily: https://www.biblicalarchaeology.org/daily/ancient-cultures/ancient-israel/jerusalems-iron-age-moat-discovered/