Isaiah continues to describe a time in the future when God will judge the earth. Prophets sometimes describe a future event as something in the past or in the present. This emphasizes the event certainly will happen. (See: [[rc://en/ta/man/jit/figs-pastforfuture]])
The abstract noun "desolation" can be stated as "desolate" or "empty." Alternate translation: "The city is desolate" or "The city is left empty" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])