Old mining camps, Indian burial grounds, sheep camps, petrified wood, quarries for projectile points, logging camps, old ranches and wagons on long trips. Basque, Peruvian, Shoshone and Chinese sheep herders.
edit- Also lots of plane wreckage, usually aluminum. And things that fall out of planes like chaff, flares and ordinance.
A couple of years ago I found a old stationary steam engine abandoned no telling how many years ago in the Uncompahgre N.F.
That and a 30's Chevy pickup at the same location.
I have hunted that area for years and never knew that was up there.
Probably logging or mine up there in the past, I am not sure why it was there to be honest.
Coz
A WW II B-23 airplane in the trees near Loon Lake in the Payette NF. A near new saddle hanging in a tree deep in the River of No Return wilderness. Old sheep camps are always interesting to see how they fashioned little conveniences. Bathtubs and hot tubs in the middle of nowhere with piped in hot and cold water from nearby hot springs.
Taking a short cut, I came across an old miners or trappers cabin once. Very obscure location. It was relatively intact, and included a chair that someone had hewn out of an old stump, complete with backrest.
Along with the little green leprechauns and little fat trolls that always steal my stuff and hide it from me, in Iowa you'll see vehicles every once in a while on the banks of rivers and in the flood plains beside the rivers due to the floods every so often. Some of the vehicles are so rusted and mangled, sometimes it's almost impossible to know what make/model it was. Or maybe the leprechauns hauled them there for scrap metal?
We've found arrowheads, spear points, Native American artifacts, Civil War bullets, clay pipe remnants, Civil War buttons and even a Union belt buckle.