Rangers in the northern Amazon in Peru have found a possible Inca citadel and stone and metal artifacts. The metal artifact appears to be a shield. This discovery shows that Amazon dwelling folks did develop metal smithing. Why the Incas could not have brought the shield themselves is not explained. The ruins are covered in vegetation. A team of archaeologists has been dispatched to the site to begin excavations.

Andina has the story here with 2 photos, one of the metal shield: http://www.andina.com.pe/Ingles/Noticia.aspx?id=kATxf6M6QRE=