There are many existential risks which would either destroy human civilisation or set us back thousands of years. Many of these risks could be mitigated by building sealed, self sufficient underground cities where humanity could survive to rebuild/repopulate the earth.
Types of risks this could potentially help with:
- super-lethal engineered pandemics/nano-plagues
- certain kinds of memetic catastrophes
- decade long ice ages or hothouse earth type scenarios
- full nuclear exchange (this wouldn’t wipe out civilisation, just europe + america + asia, so the project would only really be relevant in future scenarios where nuclear war becomes more widespread/damaging duo to tech advancement)
Key problems assuming funding/resources are available:
- Achieving a sufficient level of isolation from the external environment + self-sufficiency.
- If we’re looking at 100+ years we need a viable breeding human population. That’s is a lot of people.
- Maintaining population during long times when no crisis is evident + stopping people from breaking in when a crisis is evident (the latter is solved by having a remote enough location)
- Maintaining political neutrality + support