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As HP said, the pool locations, plus you can also go into the gym and I think perhaps the library. When you are in city view and select community lots, the little colored indicators come in two color choices. One is for the "rabbit hole" type (jobs, shops, dining, etc.) and the other for the places you can actually go in. (Not on my computer with the game, so I can't tell you the colors.)
You can go in the library. Some places (bookstore) you can see in them but can go in them. Generally the big lots I've visited you are able to go in and explore.
P.S. Library is my new favorite lot, so many different books plus free skill books!