Girls and boys are celebrating the 100th birthday of Scouting this year. Where better to hold a party than outside the British Prime Minister's home?
Downing Street is one of the most famous addresses in the world but that didn't stop 100 scouts moving in for the day to set up an adventure playground outside number 10.
Some people think of Scouting as being a bit old-fashioned, but millions of kids all over the world still think it's pretty cool because they get to have loads of different adventures.
Anyone passing Downing Street - which is in central London - on Tuesday would have had a glimpse of the sort of things they like to get up to.
There was trampolining.....
...an inflatable slide....
..and even a crazy climbing challenge.
Alex, 8, said Scouting wasn't just about having fun: "It's about having experiences you can't have if you're just an ordinary person. How many people do you know who can go outside Downing Street?"
There was an extra treat in store when Prime Minister Tony Blair came out to say hello and invited some of the Scouts inside for a spot of lunch.
...but he decided not to have a go on the climbing wall!
Alice, 8, said it had been a really special day.
Scouting is the UK's biggest educational youth group and started in 1907. There are 28m scouts worldwide and this is just the start of their birthday celebrations!