I'd use homemade clay to create a 3-D land.
Sketch your imaginary land out on paper first. Decide which landforms you're going to show and where you'll put them. Then, using a piece of plywood or other sturdy backing, sculpt your imaginary land.
As you're working, I'm sure you'll think of a SNAZZY name for your land.
You could even make an erupting volcano. http://chemistry.about.com/cs/howtos/ht/buildavolcano.htm
create a 2-D or 3 -D imaginary land. Land must include at least 5 of the following landforms: volcano, mountain range, plateau, valley, island, lake, peninsula, plain, and river to create a SNAZZY name.
2 answers
You could also use Sculpey Clay if you have a hobby shop in your town. It is cheap, easy to sculpt, and it bakes really quickly. It does come in many different colors but I have found that it is easier, quicker, and cheaper just to paint it (after it is baked) with acrylic paint. Sculpey also makes an air dry clay but it is much more expensive and not that easy to find.