I use this game when I am introducing Greece in class. It takes about 10 minutes including a class discussion. I have tables in my room instead of desks and so that works out great but even with desks it can be done for a fun time!
I give out different colored paper to each group with the name of a City-State. The groups are to put down their colored paper as quickly as possible on any empty ground space. Since the groups are so close they then have to "fight" for arable land. The simulation shows the difficulties the Greeks had due to the mountains (desks) and why they developed into city-states.