What detail is he implying with the phrase “where the railway station had been”?

The speaker is implying that the railway station is no longer in the place where it was, because it was destroyed.

Explanation:

In the phrase "where the railway station had been" the speaker the expression "had been" determines that the speaker is speaking of the past, which no longer exists. On the basis of this, we can conclude that the speaker of the phrase is referring to a railway station that no longer exists, probably that railway station was destroyed by the war and that changed the lives of the people of that place.

the first option is the answer