At/In
Phrases using "at": At home At work At school At Toffi2's place (= בבית של טופי2) Or any general place: At the opera (not necessarily a specific opera house, but also opera performances in general) At the battlefield (not necessarily a specific battlefield, but also war in general) And, not to forget: בשעה 3:30 אחה"צ is "at half past three PM".