As I look up in my apartment, I see various pipes that are suspended from the ceiling. Most of them I can easily determine where they come from and where they go. Those are the pipes that seemingly have a purpose.
There are two hanging above my living room. One has a vent attached to the end of it. From time to time, I can feel air being forced out of it. This leads me to assume that this is attached to my heating and air conditioning system. A smaller pipe extends from one end of my apartment to the other, going through walls and emptying its contents into the outside world. I followed this pipe and discovered that it disappears into the wall inside what would be my laundry room (if I had a washer and dryer). I'm guessing this would be the vent for the non-existent dryer.
In the bedroom, I have a similar pair of pipes. One is obviously the air. The other looks identical to the dryer vent, but I know it doesn't go to a second laundry closet. Because I only have the one. As far as I can tell, it also ends on the outside of my building, but its beginning is a mystery.
This mystery pipe travels through my bathroom and into my kitchen, but then disappears into my neighbor's apartment. I've been tempted on a number of occasions to go next door and knock, just to appease my ridiculous curiosity. My first thought is that it leads to the neighbor's dryer, but that hardly seems fair to me. Why should I have their nasty dryer air being pumped through my apartment? The way I see it, that pipe would be full of hot air. Heat tends to radiate from wherever it is contained. In theory, this makes my apartment warmer than it needs to be. I do notice my bedroom stays warmer than the living room. Coincidence?
Perhaps I'm wrong. Maybe it's not attached to the neighboring dryer unit. Maybe, instead, it's a pipe that only appears to lead to the outside world. Maybe it really empties into a miniature wormhole inside the outer wall of the building. Maybe it is a superhighway for miniature beings that traverse dimensions.
However, Occam's razor suggests that the simplest explanation is probably the correct one. That means it's most likely some kind of air vent. But, if one day, no one's heard from me for awhile, you may want to come check the apartment. I may have decided to get adventurous and cut into the mystery pipe. And then I'll either have been sucked into the miniature wormhole by the incredible gravity, or I'll be tied up by the Lilliputians that came spilling out of their miniature superhighway.