Construction started on 10 Downing Street over 300 years ago in 1682. It is located in the Whitehall area of Central London and is situated between Buckingham Palace and the Palace of Westminster (Houses of Parliament). Here are the floor plans of Downing Street covering numbers 10, 11 and 12. Notice that some of the floor plans of Downing Street have since changed, noticeably to the right side of Number 10.
Is you want to find it on Google Earth, search by it's postal code of SW1A 2AA.
Here is the plan of the ground floor.
Below is the plan of the first floor.
And below, are the second and third floors plans.