"The fortified city stands desolate, an abandoned settlement, forsaken like the wilderness; there the calves graze, there they lie down; they strip its branches bare." NIV translation
Isaiah continues to describe the turning of the Jewish people from religious laws to grace with a description of Jerusalem without a temple. The "fortified city" speaks of a city that is set apart which is quite obviously Jerusalem.
The Hebrew word "badad" is translated here as "desolate" but it is better translated as "set apart" as it speaks of the fact that Jerusalem will be set apart as a shining example of the grace of God. The "abandoned settlement" is from the Hebrew words "shalach" which means "send away" and "naveh" which means "home" as in home of God (the temple).
This speaks of the fact that the salvation of the Jews does not come from a building or from their efforts to be righteous. They will have seen the Holy Spirit of God dwelling in the witnesses and know that a building is not required for the presence of God.
Isaiah goes on to describe the area that is known today as the Temple Mount. His description is quite accurate as it is really not much to look at these days. Although it is ground zero in the battle of religions today, we see that, in the last days, it will be a place without religion.
It is a described as a place where calves eat branches of the trees and it brings to mind the fact that cows (and calves) do not usually eat tree branches as their stomachs are designed to digest grass from the ground. The "wilderness" meaning desert is not the normal place for a cow to live and so it desperately seeks to eat whatever is available in hopes of surviving.
This is a picture of the desperation of men attempting to be right with God through their own efforts. This is the kind of desperation that will lead men to even worship Satan during the Great Tribulation. Isaiah looks past that time to the day when Jerusalem will be a shining city built on the grace of Jesus Christ. Once again, we see that the only way to be a resident of this city is to abandon religion and hold onto Jesus.