Edge

[Xinfu]

15/11/24 A
-[...] found a vest without a detonator in a pile of rubble in the southern edge of Paris.

What does edge mean? I am not sure, because my teacher many decades ago told me, with edge, only at is used, never in.

[Rusty]

Both 'at' and 'in' work.
edge = border/boundary

[Xinfu]

Excellent answer. Thank you.
Could we also use on in that sentence based on

-a big house on/at the edge of town

[Rusty]

Yes.

[Xinfu]

Excellent answer. Thank you.