Actual bathhouses I have been to, in order of enjoyment: Steamworks in Chicago, Gym Louvre in Paris, Club Fort Lauderdale, Club Dallas, Club Indianapolis, and some sad little place down in Miami the name of which I don't remember.
Spas/gyms that might as well be bathhouses -- still operating: Century Spa in Koreatown Los Angeles is the only one that comes to mind. There is always a sexy vibe among the patrons at this place. I have only been there during the day, they say the action picks up at night.
Spas/gyms that were almost as good as bathhouses, but have changed:
Super hot memories of all three of the Lake Shore Shore Sports and Fitness Clubs in Chicago ... all three were really walking distance from each other in downtown, and the best one was on Wabash north of the river. You could go in there at almost anytime and there would be groups of men jacking off together in the steam room. Lots of cruising and playing at the one on Stetson as well, and plenty of hot guys to flirt with before finding some privacy in one of the showers. My understanding is that these places have closed, or are under new management.
Sports Connection in West Hollywood. Wow, what a scene that place was in the 1990s -- so many hot men together in the steam, sauna, and whirlpool. Will never forget being in the steam room there and making out and stroking cocks with a hot guy named Tim. There were probably ten men in the steam room at one time, and you were expected to either watch or put on a show. The action didn't stop when a new guy entered. Since closed or rebranded.
Premiere 57 in New York City. Another Korean spa, this one was good but didn't last long. Had fun in the steamroom, sauna, and spa pools. Lots of interruptions from staff, and they reconfigured it so it's not as cruise friendly as it used to be.
Peabody Athletic Club in Orlando Florida. This was a small but fully equipped hotel gym that also had full amenities -- steam, sauna, and whirlpool. Most people were not aware of it but it always had a mix of men -- a steady stream of travelers passing through and a small group of locals who used it as a gym. Staff was fully aware of the action. I think one of the hotel executives liked to use the steam room after his workout, so he made sure things stayed as they were and he liked having new playmates. You could find action there one-on-one or in groups. This one closed around 2005.