Beijing (北京 Běijīng) is the capital of the most populous country on Earth, the People's Republic of China. With a population of 21.5 million people, it is the nation's second-largest city after Shanghai. It was also the seat of the Ming and Qing dynasty emperors until the formation of a republic in 1911. Beijing is the political, educational and cultural centre of the country and as such it is rich in historical sites and important government and cultural institutions. The city is marked by its flatness and arid climate. There are only three hills to be found in the city limits (in Jingshan Park to the north of Forbidden City) and mountains surround the capital on three sides. Like the configuration of the Forbidden City, Beijing has concentric "ring roads", which are actually rectangular, that go around the metropolis and serve as good reference points as one attempts to move about the city. Beyond the ring roads are the most-visited portions of the Great Wall of China, which witnesses visitors the world over and Beijing serves as a good headquarters for those who wish to gaze upon one of mankind's more memorable and lasting structures.