3 other idiots and I decided to put on The Battle of Austerlitz at Historicon. We started a blog about it but fell woefully behind in our building process. We are scrambling to catch up as the convention is next week.
Here's the blog,
Project AusterlitzThe blog has lots of pics and write up of what/how we did the build.
Here are some pics of our WIP.

We picked up a lot of Pink foam at Home Depot

6 x 12 feet of Pink Insulation

We use glass beads to layout terrain features. It's easy to adjust them if we make a mistake or forget something. Then we draw them out with a Sharpie Pen

Carving in water features with a Dremel

Adding Elevations for the hills

Now we have to finish carving a slope in the foam.

Makes a big mess

Carving down the slope is a 3 stage process. Next step is using a Stanley Sureform

Next is sanding and it's nasty stuff to breath, so this is my dust collection system. ShopVac attached directly to sander. We also have fans venting the dust and wear dust masks.

Gluing the boards down. Low heat glue gun and bricks

Sanding done

Lightweight spackle to cover seems and smooth out elevation changes

Roads

Casting up custom sculpted buildings.
More to come, thanks for looking,
Project Austerlitz Team, Allen, Bob, Lou and myself Jeff