A rehabilitation facility or rehabilitation center was a Starfleet facility to treat individuals who were recovering from long-term physical or psychological conditions.
In 2268, Dr. Richard Daystrom suffered a mental breakdown during a simulation involving his M-5 multitronic unit and was sent to a rehabilitation facility to recover. (TOS: "The Ultimate Computer")
Individuals on medical leave could choose their own rehab facility. Nog explained this to Vic Fontaine in 2375 when he asked to remain in the Vic's lounge holoprogram for an indefinite period of time. (DS9: "It's Only a Paper Moon")