Probably one of those "Emmanuelle" movies. In Athens, Greece no less! I was 19. Even though it was softcore it blew my mind.

I think I saw "Deep Throat" on video at a party after that, and it grossed me out.
First trip to New York, back in the 1980s, I went to Times Square and visited some porn theaters and looked at Super-8 loops. The whole dirty book store thing freaked me out! Lots of creepy dudes with long black coats on -- ha ha.