What is the best sight of beijing?

In Beijing, the must seeing place is the Great Wall. Then the Forbidden City and the Tiananmen Square are worth to see. Temple of Heaven and the Summer Palace are very interesting.
If you want to know the original life of Beijing people, the Hutong Tour is suggested.
It depends on what kind of attractive spots do you want to see. There are many other modern spots and the natural spots in Beijing, too.