Beijing and the Great Walls of China

I arrived in Beijing having barely made it on my overbooked flight from Nepal (worst international airport I have ever encountered by the way). Beijing is actually quite a nice city, and if you were colour blind, you might actually think it is beautiful. I say this because it has clean wide streets, lots of trees, and some incredible sites. Unfortunately, the horrible air pollution means that everything beyond 500m in front of you appears to be in different shades of grey. The Chinese authorities have promised to remove millions of cars from the roads to improve the situation before the Olympics. I personally don't think that anything short of uninventing the wheel will make a difference by August.
Now everyone knows about the Great Wall of China, the one built over hundreds of years to keep invading Mongols out of China (see pic). Fewer people know about the much more successful wall that protects Chinese from a far great threat: free thought. Yes, when you turn on a computer there is an invisible wall that stops you going on certain dangerous websites (unfortunately for the Chinese people that includes my blog). I do certainly understand this methodology however. They could just trust their citizens not to look at these harmful sites, but in the event they didn't, cleaning Beijing's air would be impossible: imagine the pollution that sending a row of battle tanks back to Tienanmen Square would cause!