Mercy Hospital was a medical facility on Earth, located in the Mission District of San Francisco, California. This was a seven storey building with levels connected by elevators and stairs.
On the first floor, there was a nurses station, gender segregated bathrooms, and a fire hose. On the second floor, there was an operating room. It also had a security corridor.
In 1986, Pavel Chekov was taken there when he was injured following his attempted escape from US Navy aircraft carrier USS Enterprise. (Star Trek IV: The Voyage Home)