Silver Mine or Ore and Silver in Metal

Silver targets.

Giants in the Grand Canyon.

Quotes from website. 

According to an article published in The Arizona Gazette on April 5, 1909, the Grand Canyon was once home to a civilization that most likely consisted of individuals of cyclopean proportions. If such a civilization ever lived, surely it would have left behind some structure as a testament of its existence.
The article mentions the discovery of an enormous underground citadel by an explorer named G.E. Kinkaid, who stumbled upon it while rafting on the Colorado River. It is worth mentioning that Kinkaid was an established archaeologist and had financial backing from the Smithsonian Institute.

http://www.archaeologyhub.info/an-underground-city-of-giants-discovered-in-the-grand-canyon/