I am not certain why these things capture my imagination. It's a sensation that actually leaves me at a loss for words. Most of my attempts at an explanation feel flat. So here is another go at it.
I believe my fascination is the result of the overlapping of several features that pull on my heartstrings.
First is the feeling of having found hidden treasure. Most abandoned facilities have been picked clean of anything of actual monetary value. Yet they often contain items whose financial worthlessness does no justice to their uniqueness, scarcity, and storied past. These might take the shape of a piano decayed beyond repair, or Victorian architecture, or works of art (like simple murals inside childrens' quarters). The only reason these objects haven't left their home is that individuals could hardly put them to use elsewhere--they would wind up being stored and forgotten (which is hardly better than being abandoned and forgotten). What they lack in utility, they make up for in curiosity. A piano may never be played again, yet by its very presence and accessibility it continues to be a source of enjoyment--"Hey, here's a piano! Somebody once must have considered this to be a valuable thing."
Even buildings without such trifles contain something of the same character. Indoor space is not something that is constructed, or abandoned, lightly. Somehow, present value becomes an echo of past value. Why are these buildings no longer used? Why do they occupy a no-man's land between use, demolition, or embalming? Very often in modern cases the reason is mundane: asbestos. Considerations of efficiency, safety, and risk-benefit dictate that allowing buildings to rot is the least bad path.
Unfortunately this means that some of that feeling--of having stumbled upon an (available) treasure--is illusory. Everything has an owner, even if it's rotting. The state protects garbage. There will be no fly-by-night restorations, no partial re-inhabitation of a long unloved shack, no "secret place" where one can spend leisure hours in privacy. Many, but not all abandoned sites are monitored by security.
But such reminders can't quench my suspension of disbelief. Abandoned buildings will always hold the allure of offering a "secret place".
A second reason such places captivate me is the ghosts. I am not referring to the remnant souls of the dead--I am a skeptic (though paradoxically I do take paranormal phenomena seriously). When I speak of ghosts, let me be clear that I do only refer to my own projections and imaginations. Yet time is relative rather than absolute. We are not so removed from the past as the length of years would have us believe. There is a sense--whether objective or subjective, I care not--of the lingering presence of the past in the present. An abandoned psychiatric ward will always feel more ominous than a disused auto repair garage. Buildings with innocuous histories will inherit a "spooky" character from my imagination. And buildings that harbored secret crimes will not tell those secrets now.
The allure of abandoned constructs is in their stories--real, or imagined, known or projected. In those stories is an invitation to feel connected to an "other," a desire that is the flip side of enjoying the privacy of perceived solitude. There is a community that is experienced when people occupy the same place at the same time. But there is also a community that is experienced by the historian, who acquaints him or herself with people in the same place at different times. The strength of that "community," I feel, is related to the presence of artifacts--which explains in part why I find recent wrecks to hold more allure than ancient ruins.
Though to be fair, the ancient ruins are less likely to cause asbestos poisoning.
The third and last reason I feel compelled to explore our discarded places is that it recaptures a lost sense of the frontier. Over the course of months I begin to feel as though I spend my days in an endless sitcom rerun. The nooks and crannies have been exposed to the white hot light of prosaic familiarity. Everything is properly regulated and controlled.
If this sounds nightmarish, then I am being unfair. I like routine. I would be happy to surrender six days a week to it. When "interesting" events meddle in my comfort zones, I feel intruded upon.
But, dear God, remind me please that this is not all there is! Show me secret gardens, impassable stretches, unattainable heights, and dark caverns! Abandoned buildings are a part of that mystery. The once-familiar is now unfamiliar and strange; a place where the nocturnal creatures of our childhood imaginations find sanctuary from the common, and thus from becoming exploited and common themselves. In abandoned buildings the domestic has returned to the wild, the controlled to the uncontrolled, and thus, the impossible to the possible. The small world of routine becomes large again, and that one day of the week stretches out to overtake the other six in its mysteries and unknowns.
In explaining myself here I think I begin to uncover something basic to human nature, which is its longing for the infinite. That is part of the reason I can't be other than religious, and why I regard worship as one of two most vital human activities (the other being caritas, mercy). The experience of the infinite and the mysterious inside natural phenomena--like abandoned buildings--reminds me with natural feelings of the what the supernatural infinite lays before me. But one need not be religious to be captivated by the haunted and uninhabited.