Simply meeting people in a meeting room, or looking over the cubical to talk to my colleagues and discuss work.
We had a girls squad and a green tea Fridays that we had tea and chat after lunch on Fridays.
On one Halloween, we planned a pot lock for lunch with my team consisting of people from different cultures, and therefore many kinds of cuisines. We dressed up and had so much fun together.
I really liked working in an office and I have so many great memories. Now I want to build that company myself, a fun office with wonderful people, soon.