This phrase has been understood to mean either

 (1) the literal forests (see 1 Sam. 23:15), or

 (2) the royal building, which, because of its cedar columns, was called “the house of the forest of Lebanon” (1 Kings 7:2; 10:21; see 2 Sam. 7:2, 7; see on Jer. 22:6, 7).

 One of the destructive acts of an invading army, like that of Nebuchadnezzar, was the cutting down of “the tall cedar trees” and “the choice fir trees” (2 Kings 19:23). Repeated desolations of the timber of the land furnish a partial reason for the comparative scarcity of trees in modern Palestine.