On a morning walk while up North this past late summer, I noticed these architectural habitats that were not there the day before.  The intricate and delicate trap of a predator.  If you look closely, you can see the builder lurking in the funnel.    
 

This muddy castle's maker will have to remain a mystery.  Hmm.  What would be a small, yet strong, yard presence that would do this, and to what purpose?