I played in a metal band for years, so not many of the places we played were much above tolerable, but there are two places that come to mind.
One was in New York, and to be honest I don't remember exactly where it was (we drank a lot back then, you see). We crossed the then-Tappan Zee bridge heading east and took a left, so it it's up there somewhere. The place itself wasn't all that bad, but it was an old building and generally run down. It was still daylight when we got there, making it that much easier to appreciate the building and its surroundings, such as what appeared to be a junkyard right across the tiny parking lot. We went and set our stuff up and then parked ourselves at the bar for a little while. I do remember everyone there was very friendly and welcoming, which we appreciated. Some of the venues we ended up in had the stereotypical "eff you and I hate everything" vibe, but not this place.
At any rate, it's showtime. We take the stage, and, since it is now dark, paradoxically I can see something now that I could not see when we were setting up. Light was coming up out of a hole in the stage. Having watched a ton of horror movies and it never having sunk in to NOT go look in the hole, I walk over and can see the floor of the basement a good 14-15 feet below. It was lit by a single light bulb and looked like where people would end up after having been kidnapped by a drug cartel or a cult of some kind. The stage floor consisted of old planks, one of which had given up trying to support all the metal bands, apparently, and the end had broken off leaving a gap about a foot square. This did not fill me with confidence. But, we collectively managed to avoid plummeting into the void and made it home in one piece, albeit a hungover piece. Not only was that bunch friendly, they could drink.
The second, and, for me, the prizewinner for horrible bathroom memories, was a place in Philly. It was what appeared to be a converted rowhouse; two units right next to one another. The one side was actually pretty nice as metal clubs go, with a long, well-maintained wooden bar that ran almost the length of the room, and a stage that was probably about 15' x 20. Plenty of room, for once.
However, the finishing budget did not extend to the neighboring unit, which had a couple pool tables and what could be charitably described as a restroom. One old urinal, a broken sink, wet floor (which we couldn't decide if it was pee or just leaky pipes; it didn't stink too badly, so I voted leaky pipes), and a stall containing one toilet. Not much to see, really, and we all had to go shortly after arrival at the club, so we thought we had all seen what seemingly minor grossness the restroom had to offer. About an hour later the guitar player come bolting out of the bathroom, laughing and disgusted at the same time: "Dude, you have to see this!". Again, I ignore my instincts and wander into the restroom behind him. He dramatically flings open the stall door, and there, in the dry, non-functioning toilet is a trucker hat with a giant piece of human poop on top of it. I took off out of there with much haste, but not before that image burned into my brain, and worse, that smell hit my nose. For a few minutes I was actually angry at the guy: "Why the #$%& would you drag me in here to see that, man?" But a couple beers later it went from disgusting to comical.
There were plenty of shady joints in those days, but those two were the first to come up in the memory banks when I read this thread title.