The book I am reading is Because Internet by Gretchen McCulloch but she credits the book by Oldenburg for the concept and definition of a “Third Place”. She brings it up in the context of arguing that the Internet now serves as a Third Place for many people these days and I think this thread would support her.
Does discuss the shortcomings of virtual third spaces replacing physical ones?
I think physical third spaces allow more possibility of developing actual friendships with some of those people you talk to but don’t ( yet) know. These often anonymous virtual spaces much less so.
If we hung out in a tavern talking to the same group of people as much as we do here we would likely think of at least a few of each other as friends. Yet I doubt many of us have crossed that categorical line here.
I wonder if it alters the very nature of social skills in the face to face world as well.
I meet periodically with a number of friends I’ve known since Jr. High days. Typically at a (sort of) centrally located bar. This has resulted in interactions with strangers, but that’s not the intent.
If people are looking for a Third Place, volunteer somewhere. My Third Place is the animal shelter where I volunteer. I talk to a few people I know (other volunteers), but mostly I talk to people I don’t know about adopting a kitty. It’s pretty fulfilling. 
I spend the most time outside of home and work at the gym. It doesn’t really fit your criteria though, because its not open to the public and there isn’t really an expectation that you’ll have conversations with people. I am pretty friendly with a few regulars in yoga class, so maybe that counts.
Apart from that, I have
My children’s sports events. Easy to chat with the other parents in the stands, relaxed atmosphere.
The nightclub at the Arundel Mills casino. Dancers are friendly.
My language practice events. Talking to other people is the whole point.
I think for a lot of us, some part of the internet is our third place. But I think I’m going to modify the definition a little bit. A third space is not someone completely private, like your best friend’s apartment - but it also doesn’t have to be open to the general public, so a church or synagogue, the members-only gym, a fraternal organization and common areas in your apartment building can all be “third places”. It’s not just the place that comes up third on the list of “where I spend the most time” , it’s a place where people go to socialize and hang out. If the place you spend the third most time is the hardware store, but you just go in ,buy what you need and leave, it’s not a third place. If on the other hand , you hang out there for an hour or two a few times a week talking to the other regulars even if you don’t need to buy anything that day, it is. You don’t have to interact with strangers, but newcomers are welcome. Someone quoted the *Cheers *theme earlier, and that’s a good example- Cliff and Norm don’t exclusively interact with each other , they also interact with the staff and Frasier eventually become a regular at the bar.
Hmm. I’d never heard the phrase “Third Place” before. For me I guess it would be one of several restaurants or coffeeshops.
I think my Third Place would be the American Road. On my road trips I interact with a wide range of folks at National Parks, roadside attractions, museums, hotels and shops on main street. These conversations aren’t deep but overall they are quite pleasant, which is one of the reasons I love traveling.
FWIW Until I read about it, I never have either.
Better a Third Place than a Third Reich.