How Low Can You Go?

[grepper]

I have no idea how to massage this post into anything remotely related to knife sharpening, but it's pretty cool anyway.  That hole is the deepest, but not the biggest.  Apparently our Russian friends really dig digging. Here is the world's second largest hole:

http://www.slate.com/blogs/atlas_obscura..._hole.html

There are some other super massively gigantic holes to ponder too:

https://www.youtube.com/watch?v=__ffxYqUdt8

One of the mines was started in the late 1800's and dug with pick axes.  There you go.  How did they keep their pics sharp?