I use huge hay fields that are quite hilly. I do laps around the edges so I work up and down hill, I try to stay on the same track so I know there are no holes. I do some laps at the walk, many at the trot and some at a gallop. I do this several times a week (2 or 3) the two months leading up to hunt season and then if I have a week where I am not hunting I may do it once or twice, otherwise, two hunts a week and 2 jumping lessons a week are plenty to keep my horses going.
Galloping up hill I let them go as fast as they want, it can be quite thrilling. I also overcame my nerves about going downhill at speed by practicing out in the hay fields. A few years ago I read an article by George Morris in which he said whatever makes you most nervous is what you should practice the most (instead of avoiding like I normally do!). So I started adding the downhill work, first at the trot and eventually going faster and he is right (of course) I am no longer afraid, still mindful but not scared.