Mature city development has forced metropolitan rail line construction underground. In Sydney, Melbourne, Brisbane and Auckland major new underground rail links are at the planning or construction stage. Despite this trend, a review of the literature was unable to find any studies that have estimated the preference for surface versus underground travel amongst rail passengers. This paper reports the results of a 2014 survey of 347 Sydney rail users using services with some underground track. The survey asked about preferences for surface versus underground travel and found that 46% preferred surface travel, 39% were indifferent and 16% preferred underground travel. Unsurprisingly, 'window views' was the most important factor that determined a preference for surface travel. Surface travel was also preferred, albeit less strongly, for smoothness/quietness and safety. These three 'intrinsic' factors accounted for two thirds of overall preference with the remaining third due to crowding, reliability and speed which were 'route specific' factors. The survey included a set of Stated Preference questions that varied the travel time, fare and method of travel (underground v. surface). A penalty of 1.9 minutes was estimated for underground travel. Restricting the penalty to 'intrinsic' factors reduced the penalty to 1.25 minutes which worked out at 5% of rail travel time. The survey also asked about on-train activities of passengers and found that, unsurprisingly, that the underground penalty was greatest for respondents who 'relaxed or looked out of the window' followed by passengers who used the internet (possibly attributable to internet connection problems). The penalty was lowest for passengers who worked, read a book/magazine, talked to their travelling companions or used their electronic device but didn't access the internet.