My in-laws are going on Viking’s Danube River cruise next month, and I can’t wait for them to explore central Europe. Although Viking gave them a packing list to follow, we’ve talked about all the cruise essentials they should pack and what to leave behind. I lived in France during college and spent most weekends hopping around Europe, so I consider myself an expert on what to pack for hopping from country to country.  When it comes to travel bags, I always recommend anti-theft options like this stylish sling bag to keep valuables secure while sightseeing. Keeping your passport safe in one spot is also key for traveling through various countries, so this zippered passport wallet is a must-pack. Keep reading to shop the European travel essentials I recommend, along with tips for river cruises.…