This was to shew that Zedekiah should escape from the city through a breach in the wall
2 Kings 25:4
And the city was broken up, and all the men of war fled by night by the way of the gate between two walls, which is by the king's garden: (now the Chaldees were against the city round about:) and the king went the way toward the plain.
And in the eleventh year of Zedekiah, in the fourth month, the ninth day of the month, the city was broken up.
And all the princes of the king of Babylon came in, and sat in the middle gate, even Nergalsharezer, Samgarnebo, Sarsechim, Rabsaris, Nergalsharezer, Rabmag, with all the residue of the princes of the king of Babylon.
And it came to pass, that when Zedekiah the king of Judah saw them, and all the men of war, then they fled, and went forth out of the city by night, by the way of the king's garden, by the gate betwixt the two walls: and he went out the way of the plain.