根据以下所给内容，写一篇比较上海和北京这两座城市的短文，词数：100左右。

Both Beijing and Shanghai are famous cities in China. Shanghai is in the east of China while Beijing is in the northeast. As the capital of China, Beijing is the center of politics , economy and culture. It has a population of 16.33million. Meanwhile, the population of Shanghai is 15 million. When it comes to characteristics, Beijing is an ancient city with lots of places of interest,which attracts millions of tourists from all over the world every year. However, Shanghai is a modern city with lots of high buildings. The world’s third longest river----the Changjiang River flows through the city of Shanghai into the sea.