India, Oct. 17 -- A saxophonist rounds off his set with a playful trill, bows, and slips offstage. The room hums with chatter as glasses are refilled and waiters glide between tables balancing small plates of jeon and steaming bowls of late-night ramyeon. In the corner, a group of tourists debate whether to stay up to try and beat the jetlag or duck out after the next round of soju, the tension from their indecision rising above the music piped in to bridge the silence. It's close to midnight in Seoul, and a small tour will show you how the nightlife pays little regard to the working week, and the crowd shows no sign of thinning.

Outside, the city feels as if it has only just woken up. Couples wander arm in arm beneath flashing signs, of...