In a wilderness hot springs with my wife in my lap, less than 10 ft. from half a dozen total strangers! The coolest thing (for me) was that my wife initiated it!
On the third floor of a hotel at the railing of the outside hallway leading to the rooms. My wife had a long white skirt on, and I just lifted enough to get inside her from behind and draped it around to hide what we were doing. It looked like I was just hugging her from behind. There was a group of guys that walked by us so obviously we stood still, but finished once they had passed and we’re gone. They all said hello as they walked by.
In van, down by the river. Seriously though in a mall parking lot. No windows except the back and covered. Lay back watching though the windshield as the shoppers went back and forth.