Nuclear City of China, Nuclear research facility in Haiyan County, China.

The Nuclear City of China, also known as Factory 221 or Base 221, occupies 570 square kilometres of the Jinyintan grassland in Haiyan County, Qinghai. It comprises 18 factory zones (Zone A) and four residential zones (Zone B), with 564,000 square metres of buildings. Extant structures include the nuclear weapons monument, the generals' and experts' buildings, office and research blocks, the full-bomb explosion test site, the Shangxing station where the first atomic bomb was loaded onto a train, and the No. 6 sentry post.

The facility was built in the mid-20th century as China's first major investment in nuclear research during a period when the nation was seeking technological advancement. The site became central to China's efforts to develop its own scientific capabilities.

The site represents a pivotal moment when China sought to develop its own advanced technology independently. Visitors come here to understand how this effort shaped the nation's path forward.

Visitors should wear comfortable walking shoes since the site covers a large area with considerable distances between buildings. Guided tours are the most effective way to understand what each area was used for and why it mattered.

The base covered 570 square kilometres, with 18 factory zones (Zone A) and 4 residential zones (Zone B). Among the surviving structures are the General's Building and the Experts' Building where the scientists lived, the theatre, and the Shangxing station from which the first atomic bomb was loaded onto a train.