Question: This is the least interesting part of what was once the largest system of fortifications in the world, and in any case you can't get in to see it.
There is no way to get in to see the least interesting part of an old system of fortifications.

Answer: yes

Question: A day, when you'd seriously consider separating your mind from your body.
The day made you want your body and mind to stay together.

Answer: no

Question: Where did you find this? I asked Poirot, in lively curiosity.
This had been lost for a hundred years, how did you find it?

Answer:
it is not possible to tell