Hello hangar and welcome to Pixelation!
Your greatest tool for this kind of work is the usage of silhouettes. They are tremendously powerful at conveying information. Here's a quick example:
(Ignore my playing around with trees in the background)
Notice the foreground immediately stands out as rocky outcrop with grass strewn about... at least I hope it does
This can be applied to great effect on something like a ruined building, too. Find some reference photos of buildings under construction, or in the process of decay, and note the kinds of silhouettes they make... I imagine lots of support poles and wires jutting out will be a big one, as well as chunks missing and piles of rubble heaped up at areas around the base.