text: which settlements was built at a very high elevation becuase it was close to the silver mines of cerro rico in   http://www.unesco.org/courier/2000_03/uk/dici/txt1.htm  potosi, bolivia. it was a rich city in the 16th to the 18th centuries, when the silver mines were going strong and silver was being sent back to spain. today it is not prosperous. site above has photos, map, and discussion.