This next shot looks like it was taken with a fish-eye lens, but it's just the natural shape of the hills.
It's called Horsethief Park because horse thieves used to hide out here.
I would guess they were related to mining. I've got several posts to write about mining in the area as I took a day to explore that aspect of the area's history recently, including going into a mine shaft and visiting an active surface mine. But those photos are for another time!