Collapsible Rocks

So what have I been working on for the past week.  That's right terrain. I watched a tutorial on Beasts of War on how to create collapsible rocks.  So one trip to Poundland later and i had everything I needed.

See they're squishy.  But can also take a fair bit of weight.  These rocks are made of car sponge glued to some foam board, which is then painted and flocked.  Best of all they're super cheap to make.  You can get 3 sponges for £1, all those rocks there were made from one pack of sponges.