It all began as a bit of a joke. The writer and journalist Jon Mooalem started recording the walks he took near his home on a wooded island in the north western US.
And all you'll hear on his podcast 'Walking' is the sound of his footsteps, his breathing, perhaps a distant hello when he meets someone out on the trail, and a short ad or two recorded out in the field: otherwise there's no talk at all.
It's a slice of Slow Audio, an anti-podcast, the opposite of some of those crafted, tightly edited, highly produced, heavily scripted shows you'll hear.
Then the influential podcast industry commentator Nicholas Quah wrote a review, more listeners discovered it as a result, and people started looking for the meaning in what Jon was doing.
Was it some kind of mindfulness tool? An antidote to the Great Busy-ness engulfing us every day? Or with Jon's interest in nature, was it a coded environmental message?
We speak to Jon Mooalem, the host of the Walking podcast.