。
You mustn't go to places like that at night.
Literal
Night [at-に] such place [to-へ] go-[prohibition-てはいけません].
そんなところ ('such a place, that kind of place') — そんな is the demonstrative 'that sort of, such as that.' Pair with こんな (this sort), あんな (that sort, distant), どんな (what sort). The vague 'that kind of place' carries an implicit 'bad/dangerous' nuance in context.