OK, this isn't "my gym," but it might be worth noting in the few minutes I have.
I had been on a vaction to Las Vegas in late 2000 staying at the Luxor. They have a pretty decent equiped gym (for a hotel) attached to the spa. I was in town for a week and at that time the gym was open 24 hours. Since I'm not a gambler, I decided to use the gym one weekday evening about 10pm. I was done not long after 11pm and went into the locker area where I had stored my room key, wallet, etc. I only noticed a few people in the three hot tubs there and not really thinking anything about it, decided I would sit in the dry sauna. I discovered across the walkway there was a wet (steam) sauna--since my gym didn't have one of those, I thought I'd give it a go.
The heat was intense. I had never experienced such a shock and the steam was so thick you couldn't see your hand in front of your face. Once the steam-maker timed off its cycle of keeping the room a constant temperature I noticed a peculiar noise inside the room. I couldn't see anyone else, but I was sure it was the sounds of a sloppy BJ from somewhere inside the room. Although I'm gay, I am one of the most oblivious people to gay guys cruising--but the noise was clearly from two people in the room. I scanned the room--still not seeing thru the steam--and not knowing if I should leave or just sit still since I could be wrong.
Sure enough, a few minutes later on of the males made a moan that was clearly him reaching completion. Moments later, the door opened and 2 guys left. It was only later that I learned the Luxor Spa was practically the same thing as a gay bath house--especially at night since it was 24 hours.
I haven't stayed at the Luxor recently, but I've heard the antics of the spa were finally curbed when a few guys were arrested and the spa now closes early evenings. I'm sure someone in this forum could report more on the Luxor than I was aware of. Gym sex was a whole new concept to me. Being clueless myself, I have slowly started to catch on how it works--but no one can miss those old guys that don't realize gyms have real weights, cardio, & work out equipment but instead stay in the shower areas for what seems like an 8-hour shift.