In a wonderful piece lamenting the Anglosphere's fascinating taboo on exposed breasts, Conor Friedersdorf mentions something that those who have traveled abroad can find relatable.
When I was twenty I spent a summer studying in Paris. I'd somehow persuaded Florida State University to let me tag along on their summer abroad program. I ate little but baguettes and pasta so that I could afford a weekend trip down to Nice and Monte Carlo with some classmates.
It's there that I set foot on my first topless beach. At first my female classmates sunbathed in the American style. 45 minutes later they said to hell with it, took their tops off, and left the guys feeling slightly awkward and titillated for about 5 minutes, when everyone's notion of normal re-calibrated. That's how fast the mental adjustment happens.
I remember my first visit to a topless beach. It came during spent time studying abroad in Barcelona, and I'm sure many understand the feeling. My fellow Americans didn't remove their tops (at least not around American guys -- can't say I blame the women for that choice), but there were plenty of Spanish women -- young and old -- sunbathing and walking around sans the tops of their bathing suits. The inner 12 year old comes out for the first few minutes, but after you gawk and marvel at all the exposed mammary flesh, you realize that you're the one acting inappropriately.