City of Walls and Secrets is probably my favorite episode title. And what an episode! I love how Ba Sing Se has been mentioned over and over through books 1 and 2 as this great city that has held back the Fire Nation over the war, and then we finally get there and it is not what it seems.
There are definitely some parallels to some real world places, with the suppression of information and dedication to keeping their people ignorant. I think that is one of the big reasons for why it's such an unsettling episode, it's all very real.
But what a fantastic episode and Book 2 continues being consistently great.