Some of my favorite social experiences occurred at hotel bars near airports. An example was a time I struck up a conversation with a woman who turned out to be a flight attendant, and we ended up eating dinner together and talking for hours. Even gave me her phone number! It's one of those things that's only likely to happen in another setting such as a noisy sports bar. Being able to hear each other was really important; most bars where I live have bad acoustics and music blaring, which I think suppresses random conversations.

My other favorite type of bar is those at fancy restaurants. They are usually quieter, have better clientele, and are often a de facto loophole for eating dinner without a reservation.