A siheyuan (Chinese: 四合院; pinyin: sìhéyuàn) is a historical type of residence that was commonly found throughout China, most famously in Beijing. The name literally means a courtyard surrounded by four buildings. In English, siheyuan are sometimes referred to as Chinese quadrangles. Throughout Chinese history, the siheyuan composition was the basic pattern used for residences, palaces, temples, monasteries, family, businesses and government offices. In ancient times, a spacious siheyuan would be occupied by a single, usually large and extended family, signifying wealth and prosperity. Today, however, most remaining siheyuan are used as mass housing complexes, and suffer from a lack of modern amenities.
Fully developed siheyuan date back as early as the Western Zhou period (1122 BC to 256 BC), exhibiting the most outstanding and fundamental characteristics of Chinese architecture. They exist all across China and are the template for most Chinese architectural styles. Modern Beijing's population boom has made housing one of city's biggest challenges. Siheyuan today are typically used as housing complexes, hosting multiple families, with courtyards being developed to provide extra living space. The living conditions in many siheyuan are considered squalid, with very few having private toilets. In the 1990s, systematic demolition of old urban buildings took place in Beijing under rapid economic development. Siheyuan are being torn down to address the problem of overcrowding, and have been replaced by modern apartment blocks. According to the Beijing Municipal Administration of Cultural Heritage, there are over 3,000 "well-preserved" courtyards remaining in Beijing, and over 539 are in Cultural and Historical Conservation Areas. There are also estimated 7,000 to 9,000 residential courtyards left for sale in Beijing, and they are generally priced at 7,000 to 10,000 yuan per square meter. Other studies put the estimates at about over 30,000 siheyuan courtyards in Old Beijing. Preserved historical siheyuan include Lu Xun Memorial, Guo Moruo Memorial, Mao Dun Memorial, Mei Lanfang Memorial, and Lao She Memorial.