It may sound cliché, but in a crowded bathhouse, in an open play area with an audience. I've had fun in the bathhouse in my area before but it's never really crowded enough to be on the "fantasy" level of fun.
I'd love to have a slutty little bottom ass up in the middle of a room and I walk up and just slide in him. An audience gathers as I fuck his hole, encouraging me to pound harder and him to take it deeper. The horny men in the crowd rub on us, they caress my ass and down my crack as I'm thrusting, pulling on my balls and putting their fingers around the bottoms hole and my shaft as it slides in and out. I tell them I'm getting close and they get more verbal about me cumming in his hole. I let out one last grunt as I go balls deep and unload.
As I'm breeding my bottom, one of the other men starts licking my balls. As I pull out, I immediately insert my hard, wet dick into his waiting mouth. He sucks me clean while fingering the freshly loaded hole I left gaping and cum filled, tasting his fingers at the same time.
When I'm cleaned and drained, I head off to rest and recover to get horny again for the next open hole I come across!