Osijek is Slavonia's capital on the Drava River, its old town a Habsburg star-fortress of Baroque barracks and churches rather than a medieval maze.
Late spring or early autumn, when Slavonia's continental climate is mild enough to walk Tvrđa's fortress walls and sit along the Drava without summer heat or winter fog.
Order fiš paprikaš, a paprika-spiced river fish stew, or ask for kulen — Slavonia's cured, paprika-rubbed pork sausage — at a konoba rather than a tourist-facing restaurant.
Base yourself inside or just outside Tvrđa's fortress walls, walking distance to Holy Trinity Square, the cathedral, and the Drava riverbank.
Skip the fortress on a summer weekend afternoon — the yellow barracks buildings have almost no shade, and the bars and cafes inside Tvrđa don't really fill up until early evening anyway.
Read more in Osijek Travel Guide: Habsburg Fortress Walls & a Red-Brick Cathedral.