With its reasonable prices, convenience, frequent train schedule, great signage and spacious seats (compared to some other cities) Vienna has to have one of the best subway systems in the world. What's more, and what I think is also important in encouraging honesty and good citizenship, it operates largely on the honor system. There are no barriers to entering the stations but undercover U-Bahn employees do check tickets from time to time and the fine for not paying (I hear) is substantial. Just learn to read the signage and moving about the city is a breeze. This is the U-Bahn entrance at Stephansplatz with the Graben walking street in the background—the heart of the city.