The document describes the history and redevelopment of an underground data storage facility called DC4/C14. It started as a bomb shelter in 1936, was converted to an anti-atomic shelter in 1964, and was abandoned in 1991. In 2012 it underwent a redevelopment as an extremely secure, affordable, reliable, and simple underground cold storage facility for data (Version 4). The facility stores data on HDDs across many racks and regions underground, providing petabytes of storage capacity.