/diy/ - Do It Yourself

I said it before and I'll say it again:
precast concrete culverts and utility vaults

>Readily available
>Relatively cheap and easy to install. Truck with a crane drops it into place. Sections interlock and can be further sealed
>Designed to be buried
>Come in a huge variety of shapes and sizes
>Infinitely configurable based on your needs to include doorways, passageways, tunnel/manholes, cisterns, garages...

I don't know how you can't look at these pictures and immediately start planning out a bunker layout.