Surely it's everywhere?
In the traditional academic reading and writing sense, in class, in libraries, at home, in the park on a sunny day, on the beach over Easter, wherever you feel comfortable.
But in reality, we learn things all day. We walk around and see city centre maps, learning the landscape. We read bill boards, learning about companies. We watch the news, learning about politics, current affairs, history, and so on.
I listen to Radio 4 every now and then. That means I'm learning whilst I'm cycling to lectures (I also learn how much of a douche some drivers can be).
I would argue that every hour you're awake you're learning something, perhaps taking the phrase, "learn something new every day", to a new level. It might just be developing a sense of perspective, or slight building on blocks of knowledge and experiences you have, but it's learning.
[INDENT]learn·ing
Noun
"The acquisition of knowledge or skills through experience, practice, or study, or by being taught."[/INDENT]
Walking for 20 minutes down a high street is practice, adds perspective, and you will not get exactly the same perspective on it the next time you walk down, subtle as the differences in steps may be.