Why write about an outdoor square when most guidebooks will mention the underground city literally under this square? First of all you can see the sky: having your lunch there in summer is the moment of the day when you’ve left the cold temperature of your office to get some fresh and humid air from the outside world.
But more specifically, for me it’s the pleasure of observing the various crowds passing by this tiny place during the day. In the morning, it’s workers going to work with a coffee in one hand and lunch bag in the other; the place is still relatively empty except maybe construction workers who’ve started work earlier having a break. Around lunch time it’s denser – you can see a few groups of tourists pop up to frenetically take pictures of the statue and then run away to their next visit point. And at the end of the day, it’s when you feel the people being more relaxed.
My advice: grab a coffee or a sandwich, sit on the side of the statue and just look around. I always feel like a scientist observing a hive of activity.