The Fitness Center at Grand Hyatt San Francisco Union Square
The fitness center at Grand Hyatt San Francisco is mentioned by professional travelers. Of the 7 reviews that we tracked, 3 referenced the fitness center, like Gayot, Star Service and Fodor's.
Grand Hyatt San Francisco Union Square 
Gayot
Star Service
Fodor's
Gayot "The property offers an award-winning concierge, a cavernous fitness center, a full-service business center and town car service to the Financial District on weekday mornings"
Star Service "A large, well-equipped fitness center remains on the 35th floor, and guests can access it around-the-clock free of charge"
Fodor's "Watch the fog roll in from the 24-hour StayFit Fitness Center, located on the 35th-floor, which features cardio machines, yoga mats, Pilates props and more"
