The very beginning of everything is rehersal.
True especially if you do juggling, aerial or other forms of acrobatics, dancing or any kind of objectmanipulation.
In the summertime Berlin offers you plenty of space in it´s tons of endless parks.
Slacklining in Volkspark Friedrichshain, Poi and twirling in the Mauerpar especially on sundays, the weekly tuesday spinners meeting at Tiergarten, or just hanging out and doing your thing on your own.
But alas, every true Berliner knows it, winter comes and it is a bitch. Cold, wet, windy, icey, temperatures most likely around minus 15 or so you will soon become to hate the winter.
It´s fucking freezing cold and wet and ugly and suddenly you realize that your bedroom isn´t big enough to reherse the newly discovert contact staff moves you want to impress your juggling friends with on the next convetion.
What to do?
Berlin wouldn´t be Berlin, if there wouldn´t be exactly the places you are looking for.
My favorite and therefor the N° 1 on my list are the Katakomben. Once well known as an underground horstestable (you heard, underground stable, with a freaking horse elevator and all) are they now the home of every random juggler. Huge warm and clean spaces, with rigging for aerials, tight rope and special compartments for private training and ballet cater the need of any object manipulator. The training fees are really low (a fiver a day and very fair monthly fees for the juggling addict) as the space is run by jugglers for jugglers.
Highly recommended!
http://www.katakomben-berlin.de/