This is mind boggling. How deep is it? I mean, I'm sure there are areas that are a few inches deep and others that are dozens of feet, but generally speaking -

This is mind boggling. How deep is it? I mean, I'm sure there are areas that are a few inches deep and others that are dozens of feet, but generally speaking -- is this more or less than the height of a single story? Edit: And is it generally of similar depth or does it vary greatly from locale to locale?