When I saw this photograph on the Web I thought of a tower destroyed by a bombardment, and due to the angle of sight I liked the architecture. This photo was found on: http://www.imageafter.com in heading "architecture_exteriors”
The First stage is of knowing what "will be destroyed" in a coherent way. I thus advise you to print the image and cut out with the cutter and a coarse way the parts which could be interesting, but it is not obliged.
Then I create a mask on the copy of the image, and I start to remove the chosen zones with the "brushes". I thought of leaving details like remainders of parapets, contours of windows and I try to break in a logical way.
After a good routing and a cleaning of the destroyed zones, I can start to integrate the elements of ruins. For the reference images I searched in the images section of google.
Then, I increased the working area to add elements in the scene, with correct prospects for integration.
I drag the required elements in the scene and apply the mask on the unwanted areas.
I removed the excess debris from the building base by painting with black color. Also exceed the roof to give realism.