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The main resource that you need in steady state is always electricity. For light, heat, pumps. And a lot of it, especially in winter time. The rest is mostly closed loop.

If you are preparing for Collapse, ensure you have multiple independent sources of electricity available. Solar, hydro, wind. If you are in a city you are better off with a storage room full of canned food since your hydroponic plants wont give you much food after power goes out.

That's Europe for you. Usable train infra is actually a thing.

I got confused at first too. What he means is "somewhere outside on the ground level while my apt is not on the ground level, there are trains passing by which I can see from my apt". You need line of sight.

This is not mysterious tech deriving images from sound traveling through the floor. You will be out of luck with your underground subway.