Is there an idiom that can be used to describe the specialty of a situation/object?

For instance,

the <best part> of living alone is the privacy.

Is there an idiom which can be used for such a sentence?

I'm looking for a rather well-known phrase originating from literature, like how 'Achilles' heel' is used to describe a fatal flaw.


How about the well-known idiom silver lining?

M-W: a consoling or hopeful prospect

Cambridge: an advantage that comes from a difficult or unpleasant situation

The Free Dictionary: a consoling aspect of a difficult situation

Your example:

The silver lining of living alone is the privacy.