An embassy is a building or compound utilized by one government, within the territory of another, for the purposes of diplomacy. Embassies are generally in capital cities, while smaller consulates are found in other locations. Embassies and consulates are also referred to as diplomatic missions, and are considered the sovereign territory of their operating government, regardless of their location. Thus, an individual traveling in foreign territory may take refuge at their government's embassy or consulate.
Many worlds and galactic powers have embassies on Earth, and the United Federation of Planets maintains embassies and consulates on its member worlds and colonies and those powers and planets with which it maintains diplomatic relations.
During the 22nd century, the Vulcans maintained consulates in Berlin, Canberra and San Francisco. Likewise, the United Earth had an embassy in ShiKahr on Vulcan, which was bombed in 2154. (ENT: "Fusion", "Terra Prime", "The Forge")