Asking about location: which area or part (whereabouts).
この町のどの辺に住んでいるの？
Which part of this town do you live in?
会場のどの辺に行けばいいか教えてください。
Please tell me which part of the venue I should go to.
事故は駅のどの辺で起きたの？
Where around the station did the accident happen?
Asking about extent or degree: how far/what point (how much).
仕事はどの辺まで進んでいますか？
How far has the work progressed?
予算はどの辺を見込んでいますか？
What kind of budget range are you expecting?
レポートはどの辺まで書けている？
How much of the report have you written?