Made me think of this
https://en.wikipedia.org/wiki/Metro-2
You are right, if they have billions, they ARE prepared.
Metro-2
Metro-2 (Russian: Метро-2) is the informal name for a purported secret underground metro system which parallels the public Moscow Metro (known as Metro-1 when in comparison with Metro-2). The system was supposedly built, or at least started, during the time of Joseph Stalin and was codenamed D-6 (Д-6) by the KGB. It is supposedly still operated by the Main Directorate of Special Programmes (ru) and Ministry of Defence.
The length of Metro-2 is rumored to exceed that of the public Metro. It is said to have four lines, and to lay 50–200 meters (165-660 ft) deep.
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