The primary headquarters for the Mos Eisley Police Department was the Mos Eisley Police Station, which locals often called the city jail, and it functioned as the primary detention center for individuals arrested by the department. By the time period of 0 ABY, the jail's capacity was exceeded due to overcrowding.
Floor plan of the Mos Eisley Police Station
Despite being a relatively modest facility for local law enforcement situated within the city's central spaceport, its holding cells were utilized by stormtroopers in 0 BBY to imprison the Tonnika sisters (who were actually Shada D'ukal and Karoly D'ulin in disguise) on behalf of Grand Moff Argon. Furthermore, at least one officer intended to detain BoShek there, acting on orders from the Imperials. Big Bunji was at one point an inmate at this location.
In addition to its holding cells, the building also featured a storage area for food supplies, a room designated for inspecting the weapons of those arrested, and a space specifically designed for questioning prisoners.