The Mystery Holes of Peru

I saw this very cool story somewhere on the intertubes today but I can't remember where. I'll update with a link if I remember. (For now, via.)

A series of holes, usually about 24 inches across and in neat rows of from nine to twelve, stretched for almost a mile in Peru. It starts at the base of a mountain and then climbs up the side and meanders up and down, over some of the roughest terrain.

Nobody seems to know why they're there. Got any ideas?