Oiapoque lives in the the Brazilian popular culture as the end of their long coastline, starting in Chuí.
From French Guiana:
If you are coming from French Guiana or leaving Brazil do not forget to visit the police station - located down-town and on the bridge - on your way in and your way out to get your passport stamped. The police stations down-town in Oiapoque and St George are open everyday from 8-12 and 14-18. By car you can pass immigration on both sides when crossing the bridge. It is open Monday to Friday 8-12 and 14-18 and Saturday 8-12. Sunday it is closed.
The main square is being refurbished, restaurants, bars, and clubs have been temporarily relocated on the out-skirt of the city, meaning that a taxi ride is needed to reach it from down town where most of hotels are.