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Footage shows China's mysterious unnamed city, which goes by the code name 404, located in northwestern China in the Gansu province, Monday.
The city, which cannot be found on any map, was built in 1958. It was named after the company 404 Co. Ltd owned by the China National Nuclear Corporation. The city was established to be China's atomic bomb base and was was home to scientist and experts who carried out nuclear experiments and successfully detonated their first nuclear bomb in 1964.