In the first article below, the writer Deborah West provides an overview of the work of Dr. Semir Osmanagich in the Bosnian Archaeology Park (i.e. Bosnian Pyramids).
The second article is Wikipedia essentially denying that the formations could possibly be anything but natural formations.
The third link is to a documentary on the topic.
Are the Bosnian Pyramids the remnants of an advanced ancient civilization or naturally occurring hills with somewhat flat sides?
Help find out by examining the evidence and providing links to additional resources in the comments below.