The Atlantis Sports Club & Spa recently opened at 44 Middlesex Turnpike inside of the DoubleTree Hotel. The fitness center also features a pool and tennis courts. It's interesting to see a Bedford hotel open it's fitness center to local residents and nearby employees. The Burlington Marriott has offered membership to it's fitness center for many years.
Atlantis has 9 locations (7 in the Boston area and 2 in the New York City area). All of their locations are located in hotels.
In many cases, hotels outsources their fitness center/spa to an outside company. The outside company usually renovates/expands the center at their cost and markets it to nearby residents and employees. The outside company then pays rent for the space and typically will share a portion of the revenue it receives from members with the hotel. Depending on the arrangement, the fitness center may get a different name than the hotel.
Stay tuned for more details.