What was going on here?
Is this where Ana grew up or learnt to play tennis or something?
The place is her high school gym, and yes it's the place where she learned to play tennis. The Principal of the High School ("Mihail Cantacuzino Collage" from Sinaia pics
) where she learns made her a suprise, she brought all the students and the teachers in the gym to watch one of Ana's games, and she saied she's really pround of Ana (she was no. 2 in junior rankings at the time)