I heard that you should do hill training regularly, but I'm replacing it with climbing a nearby mountain for about an hour and a half every Saturday. I'm not sure if this is enough to replace hill training.
Still, it's much more fun than running on flat ground. I went about 4.5 kilometers and then came back, but I tried a different return point today. This course was also good because it's a course where you can run lightly while recovering after you go down for about 1 kilometer.
Next time, it might be fun to go up the mountain all the way and return by subway instead of coming back.