The U.S. Embassy in London's Grosvenor Square, an elegant square situated south of Oxford Street. It's been in the same place for years, so long that they use the term Grosvenor Square to refer to the whole of the embassy, just like you would say "today London decided to..." to talk about the English government. The former embassy was used until the 60's, when it was purchased by the Canadian government. The Canadian government is still there, in the building they've named the Macdonald House. The new US embassy is on the west side of the square. It is a huge building designed by the architect Saarinen, completed in 1960. It's modern style has been criticised because it doesn't integrate very well into the Georgian style square. Since 2001, they have installed new anti-terrorism methods, but you can't tell as much as in other countries, even though the street is closed off to traffic. The square has been the site of the embassy since 1785, and during World War II, Eisenhower had his military offices there as well.
The Embassy of Germany, like other international embassies, is a diplomatic mission. The German Embassy represents the country of Germany abroad, and provides information related to visas for those who would like to visit for work or tourism.