One of the must sees of Annaba is the Church of Saint-Augustine of Hippo, or "Lela Bouna" as it is sometimes reffered to in Arabic. It is on a hill not too far outside downtown, and it's a dominating sight. Taxis run regularly to and from the church. The Church itself is a marvel, with stunning architecture and ancient Roman ruins right behind it. Saint Augustine's hand is kept inside the church.
Downtown Annaba is a great place to take a stroll. Visit "Le Cours" the central square in downtown and try some delicious ice cream sold at local cafes. Walk around downtown and be surrounded by French colonial architecture and stunning contrasts of old and new. Just off Le Cours is "La Place d'Armes". The oldest part of the city the Kasbah, it boasts magnificent Ottoman architecture and was build starting in the 12th century. Enjoy narrow alleys and walkways and marvel at the fact that people to this day still live in these houses. It is on a hill and at the bottom at the entrance of La Place d'Armes is a mosques built by the Turks in the 16th century.