One wall is devoted to Bad Government, a gloomy portrait of Tyranny, badly damaged, and the other two to Siena's own enlightened Good Government, full of fascinating detail of town life roof-builders, shoe shop, school, outdoor tavern, ladies dancing in the street and hunters riding out to the surrounding countryside.
Both walls depict a utopia of a good government. 
mnli hypothesis: Both walls depict a utopia of a good government.  premise: One wall is devoted to Bad Government, a gloomy portrait of Tyranny, badly damaged, and the other two to Siena's own enlightened Good Government, full of fascinating detail of town life roof-builders, shoe shop, school, outdoor tavern, ladies dancing in the street and hunters riding out to the surrounding countryside.