government office building
Refers to the physical building housing a government agency, such as a city hall, prefectural office, or national ministry building.
The new city hall was built near the station.
Let's meet in front of the prefectural office building.
The city built a new government office building near the station.
This government office building is deteriorating badly with age.
The prefecture announced a plan to relocate its government office building to the suburbs.
官庁 refers to a government agency as an organization or institution, whereas 庁舎 refers to the actual building it occupies.
庁舎 and 校舎 share the character 舎 and sound similar, but 庁舎 is a government office building while 校舎 is a school building.
庁 (government office) + 舎 (building). A straightforward compound for a government building.