Most of us use it. We all love to hate it, but secretly… we love the underground tunnels, the funky smells of the U1 stations, and the Karlsplatz passage maze. But how well do you really know Vienna’s U-Bahn network? Who is the most traveled amongst us, that has ventured to all pockets of the underground world and experienced the far reaches of Vienna’s metro lines. Put yourself to the test with this quiz.