In my pants at a playground as a teenager, crawled into one of those semi-circle tunnels and let loose
Public park bathroom floors, I’ve done many times. They’re already vile and neglected but that sort of location really turns me on. Me and friends with similar tastes loved pissing and pooping in them.
My grandfather had a big garage that he repaired cars in, but his business was defunct. He had a sort of abandoned, tiny bathroom in one corner. When I was young and living with him, I’d go there to mess in peace.
Lots of other possible places, odd locations is a huge turn on for me