The Fitness Center at Radisson Blu Hotel, Prague
Sheraton Prague Charles Square Hotel's fitness center is praised by writers. Of the 3 reviews that we monitored, 2 recommended the fitness center, like Star Service and Oyster.
Radisson Blu Hotel, Prague 
Star Service
Oyster
Star Service "The fitness center finds favor with active folk, offering a well-equipped gym, sauna and whirlpool, and the small spa has a pair of treatment rooms primed for massages, manicures and pedicures"
Oyster "A variety of features include a French restaurant, late-night bar, and seasonal rooftop terrace with panoramic views, plus a small spa, 24-hour fitness center, and meeting rooms"
