simple:Embassy

A foreign embassy is the official diplomatic office of one country in the capital of another country. It is the official office of the ambassador of the home country, serves as the primary channel of communication between the two governments, negotiaties treaties between the home country and the host country, and promotes economic and cultural exchange between home country and host country.

Many Commonwealth countries, by virtue of tradition and the technicality of sharing a common head of state, do not exchange embassies and ambassadors but high commissions and high commissioners, which are identical in all but name.

See also: Consulate general