Several European cities are making money by offering tours of their sewer systems, according to the Wall Street Journal. Because we are always looking for city-university partnerships, we could package the city sewer tour with a tour of UW-Madison?s underground steam tunnels. The labyrinth of campus tunnels was first constructed in the late 1800s. They are not open to the general public, but people have been known to explore them anyway, most famously a guy nicknamed “Tunnel Bob,” who startled students across several decades when he stuck his head – adorned with a Packers cap – out of various tunnel entrances.