I grew up in a suburb. It had once been a small town but had been swallowed up by a nearby big city. However, it still had that "small town" feel about it and life centered around our local community, not the city. During my junior and senior years in high school (11th & 12th grades), I used to go with a buddy of mine to the local gym. We'd usually go in the evening when things had emptied out a lot and there wasn't so much of a hassle, but when we'd go earlier in the day it was like the OP described; you'd see lots of men in the showers who you'd see around town. Saw a couple of my teachers, the owner/manager of the hardware store where I'd worked after school or during the summer, the pharmacy owner and city council member whose daughter I'd dated, the local newspaper publisher and editor, our insurance agent who played golf with my father, my barber (who I later found out had a record of "public indecency"), and the good-looking guy across the street who's dishy wife was having afternoon flings with his best friend. I one time saw him there with his friend and, even then, I remember noting that the friend was a lot better hung and speculating on whether that had anything to do with his wife's cheating.
It was also hot that it was a two-way kinda thing: Our family was fairly prominent in town (there was a street named after my grandfather), my mother was very active in community affairs, and I was a star of the high school football team, which was a really big thing there. Our games were covered like the NFL in the local paper. So it was kinda hot knowing I was also somewhat of a local celebrity and that, in a similar fashion, a lot of the eyes were probably trained on me. Kind of scary in a way. Everyone would stop and say "Hi" and "How's your father?" and things like that. I remember feeling very self-conscious in the showers and locker room, since though a big strapping guy, over six foot at the time (now 6'3"), I'm hung like a chipmunk and particularly tiny when soft. I was just sure they were all checking me out down there, and remember being bothered by the idea that they might be thinking my father was also poorly equipped (which he wasn't).
My work subsidizes membership in a nearby health club. I see lots of guys there from work and company sports teams I play on, a few work "competitors" or "rivals", some bosses, and even a couple of my employees. It's kinda hot seeing what the other guys are packing and then seeing them back at work with that memory in the back of my mind.