Two, mostly: trash and abandoned buildings. Trash because it is indicative of humanity, you are never too alone if you find trash. That, and many other things, like how it all litter tells a story, or the odd fact that you never find garbage more than a year or so old.
Now, abandoned buildings.
The closest I can come to describing the feeling of standing within an abandoned building is somewhat akin to standing in a sort of raft. But, imagine the raft has more patches than original fabric, more holes than solid barriers. Imagine that you are standing amidst the largest, vastest ocean, but that the beautiful blue waters are actually years, decades of age, slowly but surely waltzing confidently through the patches.
Imagine sinking so slowly that you can’t physically see it, you can only feel it in your bones or deeper still, at the core, in your marrow. Your mind and your body fight: are you actually sinking? If so, could you save this raft, - take it back to land, fix it anew?
And then the lobes of your mind are precisely and methodically separated by one sole realization: the raft and the ocean do not care at all. As you question, as you float from thinking of the beauty to shivering in terror, the raft slowly bobs along. Up, and down, then up again - slowly, surely, without thinking. As it has done, for thousands before, as it will always do until it bobs too close to the waters edge. Then, without feeling, it will do whatever comes next, be it sink or float.
Slowly. Aimlessly. Without thinking.