What about something a little bigger than an encounter, but smaller than a city or region? Something like "design a dungeon or wilderness area map, one that implies multiple exciting encounters."
Every time I read "...believed to have been forged from a unicorn horn in the eye of a hurricane on the night of the full moon" (or whatever) I think: I don't believe that. I believe my 10th level wizard can make it in the comfort of his own home whenever he has some downtime.