The reference is to a parcel of bushland that belonged to the king, from which mature trees could be harvested. As a curiosity, the term translated as forest
is a Persian word that gave rise to our English word paradise.
This forest’s location is unknown, though obviously it would need to be close enough to Jerusalem to make transportation of its logs to the city possible.
8 and a letter to Asaph, the keeper of the king’s forest, that he may give me timber to make beams for the gates of the fortress of the temple, and for the wall of the city, and for the house that I shall occupy.” And the king granted me what I asked, for the good hand of my God was upon me.