The wife and I find that having sex in a public place with a chance of getting caught to be both stimulating and exciting, it definitely adds a thrill to the act . What are your thoughts and where have you done it.
My wife and I have fucked at Black's beach in San Diego. It was in a semi secluded area but there were still people watching. My wife liked that several men were watching and masturbating. I took her doggy style.
The most public place wife had experienced sex, well, if you mean open spaces then it was around the trees of a belvedere/lookout near where she lived while single.
But public in the sense of risky and exposing was in a bus station with a man she used to go out (already married).
Both of us (husband and wife) it probably occured sometimes we had sex in tree parks.