The urban area of Beijing is in the south-central part of the municipality and occupies a small but expanding portion of its area. The core city districts are surrounded by urban districts, which in turn are surrounded by suburban districts. The northern part of the municipality contains less populated counties. The inner city, which was walled off in ancient times, is divided into eastern and western halves by Dongcheng and Xicheng Districts. Dongcheng contains Tiananmen Square and the Forbidden City, which form the center of Beijing and are the former home of the Ming and Qing emperors of China.

From the center, Beijing spreads out in bands of concentric ring roads starting at the Second Ring Road; the outermost Sixth Ring Road passes through several satellite towns. The Ring Roads are commonly used as reference points. Four other main districts, Haidian, Chaoyang, Fengtai and Shijingshan, were once considered on Beijing’s outskirts but are now integral parts of the city and within the Fifth Ring Road. These districts contain the CBD and the Olympic Green. Suburban Tongzhou and Shunyi to the east are rapidly urbanizing and popular with expats.

Downtown Beijing has several lakes. During the Yuan Dynasty, the Mongol rulers expanded them and built the imperial palace of Dadu around them and subsequent emperors of the Ming and Qing dynasties used the lakes as imperial gardens, although today they are surrounded by popular bars and cafes.

Source: http://expatessentials.net/beijing-preparations-cityscape/