The answer is holes that present a hazard to runners on the Glacier Haute Route, as seen in this image by Swiss photographers, Dan and Janine Patitucci.
Pascal Egli and Kim Strom look into the depths of a 'moulin' on the d’Otemma glacier while running the Glacier Haute Route.
These massive holes stopped us in our tracks while traversing the glacier: You don’t want to get too close, but you can’t help looking down before cringing and stepping back.
The holes are carved by surface melt water created during warmer times of the day - sometimes as white water, before it finds a weakness and disappears into the ice.
At work and play
We are fortunate to call the mountains our workplace and still marvel at what we get to do on any given work day, be it in the Alps or Himalaya.
After all these years, the passion we have for life as mountain sport athletes and photographers hasn't faded. Experiencing the Alps on so many levels keeps us motivated for what comes next.
Each week over the next few months, swissinfo.ch is publishing a series of Dan and Janine Patitucci’s pictures from the past year: images of unexpected encounters and grandiose landscapes that put us humans in our very small place.end of infobox