Look for the famous, yet understated black door on this notable street that bears the number "10." It's the residence and office of England's Prime Minister. It has been a beehive of activity through two World Wars as well as during countless celebrations and crises that have affected the British populace. It first became associated with the office of Prime Minister in 1730, and so far, 52 men and one woman serving as PM have called #10 their home at some point in their lives.