We were not in Europe but I took a larger model, 1-1/2 liter hydration Camelback pack with water that was stuffed with granola bars, wet towelettes, beach towels, camera, and personal items. No one physically looked at it or it's contents...but I think it did go through Xray(?) I liked it because it was hands-free traveling. The kids ran out of their bottled water and were drinking water from my hydration pack during out hot day trip to the ruins. I like to eat out and enjoy a "foreign" meal when we are in new cities/countries so we budget for it.