The most amazing thing about Number 10 is how big it is.
It's got loads of rooms filled with ornate furniture and valuable paintings where they hold meetings and parties.
There are also lots of dull-looking offices too!
One room is supposed to be haunted by a woman in a long dress and pearls.
There are corridors which mean Tony Blair can get to different government offices without going outside!
It has two identical front doors so that whenever one needs a lick of paint, the other can be put in its place.
Get this too - the prime minister doesn't have any keys - instead there is always someone on duty to let people in.
And in fact, Mr Blair only uses the house for working - there's more space for him and his family to live next door at Number 11!
You can take a tour of Downing Street at Mr Blair's website http://www.number-10.gov.uk/output/Page1468.asp