10 Downing Street London SW1A 2AA United Kingdom
Downing Street 10, also known as "Number 10", is the official office and residence of the British Prime Minister, and has been such since 1735.
Downing Street 10 is not open for public visits, but you can take a virtual tour on the official UK Government webpage. Did you know there is one more official resident at Number 10? He is a Chief Mouser, and lives in famous Downing Street building since 2011.
When you are in London, you can pass by Downing Street 10 if you decide to take a walk from Trafalgar Square to Big Ben. If you are taking a Big Bus sightseeing tour, it is stop #12, Whitehall, for Churchill War Rooms, Downing Street, Changing of the Guard and the Cenotaph.