Originally Posted by
SKT-DK
I think the garden you are referring to might be the area at the juncture of the main D wing and A, landside (visible from the TG domestic lounge which is facing that side). Does that sound about right?
To my knowledge there is no garden-like area airside, so this is my best guess

Could be right. This video (it's only 2 minutes) shows it at a juncture, and this is the Google view of the area.