observation room
A room for observing patients, suspects, or subjects, typically in a hospital, police station, or research facility.
The patient was first shown to the observation room.
We monitored the suspect from the observation room at the police station.
監視室 emphasizes surveillance or monitoring, often with cameras, whereas 観察室 is broader and can include direct human observation.
Compound of 観察 (kansatsu, 'observation') and 室 (shitsu, 'room').