What is the given circumstances in scene1 of Othello?
Othello Act I, scene i takes place at night in Venice, outside the home of the city-state's senator, Brabantio, father of Desdemona. He has been having bad dreams about his daughter.
Outside, Roderigo and Iago learn that Othello (a black Moor of close to 50) and Desdemona (a white woman of 20) have secretly eloped and married. Apparently, Othello knew her father wouldn't approve of the interracial marriage, so they perform the ceremony secretly. Also, Othello has appointed Cassio as his lieutenant, skipping over the now jealous Iago.
Iago urges Roderigo to wake up her father and tell him the surprising news, knowing he will be angry and try to annul the marriage. Brabantio is baited by the racist Iago's ploy, but when he looks down from his balcony, he only sees Roderigo. We realize that Iago is the real villain, hiding behind his pawn Roderigo.
Also note is that Venice is at war with the Turks, and the senate has had a secret war council that night and appointed Othello as their General against the Turks at Cyprus, an island on the Mediterranean. So, we know that the rest of the play will take place there.