The medical centre of Deep Space 9, located on the Promenade and run by Doctor Julian Bashir, combining a small surgery and ward with the station's main medical research laboratory.
The Infirmary is Deep Space 9's hospital, a compact Cardassian-built facility opening directly on to the Promenade. Julian Bashir takes charge of it on his arrival in Emissary, when it has been stripped and vandalised by the departing Cardassians, and he runs it for the whole of the series with a staff of Starfleet and Bajoran nurses.
Much of Bashir's research is carried out there, including his work on the aphasia virus in Babel, his attempt to remove Garak's cranial implant in The Wire and his search for a cure for the disease afflicting Odo in the final season.
The Infirmary also treats the wounded of the Dominion War, and it is where Vedek Bareil dies in Life Support and where Bashir fails to save Jadzia Dax in Tears of the Prophets.