The city in this painting is  in ruin and you need to move a bit to see all its part, as it happens in the “heavenly city” paintings (It plays with perception and the concepts of memory as an action that requires effort).
But also the bomb has yet to go off.
In addition to the imminence of the explosion suggested by the title, this shows, in relation with the already destroyed city down below, that actions have consequences well before the devastating events that they entail.