I don't have personal experience with sheep, but think about where sheep live in Europe: I think of Scotland and Ireland and the Pyrenees. They do very well in hilly areas. I remember spending about an hour with my mom, standing at the bottom of a huge hill in scotland, watching border collies drive a flock of sheep straight down the edge of this small mountain. The farmers drove the dogs up to the top of the hill, then got in their car and drove down the windy road to wait at the bottom while the dogs took the sheep straight down the very steep side. It was amazing.