I opened the balcony door to look at the lasers in the sky and there was a cat meowing on my balcony (note I am 11 floors up). I've seen this kitty before but last time, I had my door open and I didn't notice it had come in to check out my apartment and it ran out when I turned around and noticed it.
This time it meowed and invited itself in for a poke around. I think it checked out every inch of my apartment then left politely (I left the door open so it knew it could leave). It turned back up 30 minutes later so I opened the door again and it again came in meowing at me and rubbing against my leg, and exploring more. I felt it had probably explored enough after 15 minutes and walked it out but it's still sitting outside my door looking at me.
From one of the apartments to my left. Not sure which one. There are partition things with cat-sized gaps it can squeeze through so it can explore other peoples balconies.