took up residence in the fortress: After capturing the city, David made the fortress in Jerusalem his home. Jerusalem was a practical place for David to rule the expanded kingdom.
The city was centrally located and neutral, lying on the border between Judah and the northern territories. Its strong natural defenses and water tunnel were especially important during a siege (an attack meant to surround and cut off a city).the supporting terraces: See study note on 1 Kings 9:15.