I have read of the "Gardens of the world-Marzhan" site, here in a post dated in early April.
We also glanced at (due to lack of time; we do plan to go back)the estate around Schloss Charlottenburg on our only previous visit.
And I have read of a Tulip Festival in the Dutch Quarter of Potsdam (not Berlin!) on Sat and Sun 19th and 20th April.
Are these the 3 best in class, so to speak or can anyone recommend any other worthwhile park/garden which is equal to or of greater "value" than the above.