I always thought (and still do!) it's about whether there are moments when both of your feet are off the ground, not about the pace.

Lots of change in elevation, with steep hills, stairs etc. For comparison my resting heart rate is ~57 on average, and for more intense workouts I can go up to ~160 for periods of time, so I think my range is healthy. But I can get a lot out of a brisk walk in this terrain ;) I've found it's a lot better for my knees than running or jogging, which I've practically replaced in favor of mountain hiking and said brisk walks, as well as indoor cycling when the weather is bad.