Traveling across Europe by rail may be a rite of passage, but it isn't exactly a five-star experience. Enter the Danube Express, a new luxury hotel train. With trips like an 11-day odyssey from London to Istanbul and deluxe sleeping cars that feel more like suites, there is the opportunity to explore the Continent in comfort. Prices start at $1,741 for a three-day excursion through the Balkans.