。
You really know your geography, don't you.
Literal
You [topic-は] quite geography [to-に] bright [sentence-final-な].
~に明るい ('bright in / well-versed in') is an idiom meaning 'knowledgeable about.' なかなか here means 'quite, impressively' — it adds a note of genuine admiration. The sentence-final な is the masculine reflective/confirmatory particle, giving it the tone of an impressed observation rather than a question.