The PCs are stuck in a town with a strict peace policy, the tiniest scuffle can land you years in prison. The town also happens to be a tourist haven, so inn-prices have skyrocketed. The only way the PCs can rest is if they splurge on a room, with their enemy.
This really comes from an ancient Chinese novel. Imagine during the PCs' travels, they come to a place where the gender roles are completely reversed. What adventures will the PCs encounter in such a place?