Non-commercial gyms with a smaller, more "hardcore" environment?

Looking for smaller hole-in-the-wall gyms (so not EoS, Planet Fitness, LAFitness, Mountainside, etc.) with a smaller and more "serious" atmosphere. No disrespect to EoS or any of those gyms, I've used those for years, but I like the gritty and "dingey" vibes of smaller, more old-school gyms.