Not just where people run but where they record doing anything. The Adirondack High Peaks yield what one would expect: the trails are used pretty much in proportion to their ease in reaching summits. Zooming in on Allen Mountain one can see a low use spur. The herd path to the summit turns off Allen Brook to the left (turning north slightly to go roughly due east) while the brook continues southeast. It's a turn that's often highlighted in descriptions because it's easy to miss. Clearly some did.
It's a population heatmap merged with roads and trails that are easy to run (or do other activities) on. Zoomed out it's just a heatmap, but zoomed in shows local nuances.
Click it. You learn, for example, that someone in Fort McPherson not only runs but installed Strava and used it the one time it usually takes to stop using Strava.
your monthly reminder that strava for road running kicks the shit out of strava for biking