city hall; municipal office
The administrative building or office of a city government. Used for the physical location and the institution.
I went to the city hall to get a certificate of residence.
市役所の窓口は午後5時に閉まります。
The city hall counter closes at 5 p.m.
After moving, I completed the address-change procedure at city hall.
I submitted the marriage registration to city hall.
I inquired with city hall about the detailed procedure.
市役所 is the city government's administrative office building, whereas 公会堂 is a public hall or auditorium used for events, not for government business.