Vukovar is a Croatian symbol of resistance, which you'll better understand after the city tour showcasing the Ovcara Memorial and Eltz Castle. Alternatively, choose a wine tasting in Ilok, a center of wine production since Roman times, where you'll sample its famous Grasevina, Traminac, and Frankovka wines. Back on board, cruise to Novi Sad, sometimes called the "Serbian Athens." Discover Novi Sad on a walking tour to Dunavski Park and through Stari Grad, the Old Town center. If you prefer a more active exploration you may choose to join a guided biking tour or hike through Fruska Gora National Park. During the evening, visit Petrovaradin Fortress, a mighty stronghold no enemy has ever breached.