Behold, is it not of the LORD of hosts that the people shall labour in the very fire, and the people shall weary themselves for very vanity? The people shall labor in the very fire - All these superb buildings shall be burnt down. See the parallel passage, Jeremiah 51:58 (note), and the note there.
Shall weary themselves for very vanity? - For the gratification of the wishes of ambition, and in buildings which shall be brought to naught.