Hi,
I was wondering if there's a term or expression in English for what in Italian we'd call (if that were to be literally translated) an "
administrative island". A quick search on google seems to suggest that this expression exists, but with a meaning different from the one I'd want to convey.
Municipalities are administrative units; their territory can be displayed on a map by means of borders. Usually, in a map we have one polygon for each municipality. Now, let's say that a part of this administrative unity is completely separated from the rest, but it is not an island in the sea or in the middle of a lake/river ... this is quite common in Italy for historical reasons. What would you call it?
(If my attempt to describe what I'm looking for does not make any sense, please feel free to ask for more information

).
Many thanks in advance!