Unusual man made structures encountered on the trail

Ever come upon a strange structure in the woods? The most common structures I've encountered are branch teepees and inukshuks.The following items were on the way to caches. I've photographed some 2010 sightings:

A splash of colour in the winter

Many inukshuks lining a secondary trail.
This photo doesn't show them all but there were
probably 50 small inukshuks about 15 feet apart.

A wreath of branches carefully laid around this tree. Side view.

The wreath. Front view.

A pyramid of milk crates. The center, top most crate is yellow.
The crates were bound together with zip ties.
I came back 2 weeks later and the crates were gone.