An easy challenge to describe -

Make a regional map in the style that was made so famous by Tolkien - drawing mountains, rivers, lakes, roads etc as close as possible to the way he might have drawn your map for you.

You don't have to draw any 'unfeasible' river systems if you don't want to. In fact you could even map a real world location in his style, as Callum Ogden has done here on his page. (link originally provided by ChickPea)

The only rule is that you are not allowed to map a region that represents any part of any of the novels he wrote.