Guys,
This is what I mean about parchment. It was the main material for western cultures to write on till about the late 16th century, coinciding till about the time the printing press came about. The result, almost any hand-made medieval map was painted on parchment not on paper.
This is the only place that sells real parchment: http://www.pergamena.net/index.php
It is essentially stretched, dried and sanded goat, sheep or calf skin.
It looks neat. The constitution was made on parchment. Much more robust than paper. Its funny, because of modern craft stores, when people think parchment they just think stained paper.

Here is a famous map painted on parchment:http://www.bodley.ox.ac.uk/users/nnj/GoughMap_large.jpg
this is what medieval maps would look like