Sounds like a great project.

You don't say what age group you are working with but I think these sources will help you.  You can modify them to the group to which you are working.  I would love to see the final result and process to share with others. 

How to Build a Topographic Model University of California (Berkeley)

http://www.ucmp.berkeley.edu/fosrec/Metzger1.html

National Geography Maps (Type in Poland)

http://www.nationalgeographic.com/resources/ngo/maps/

Newton’s Apple

http://www.ktca.org/newtons/15/kidsmars.html

Topographic Map Unit Plan (High School Age Group)

http://www.srellim.org/topounit.htm