A common challenge to the design of digital tabletops for public settings is how to effectively invite and guide passersby--who often have no prior experience with such technology--to interact using unfamiliar interaction methods and interfaces. We characterize such enticement from the system interface as the system's discoverability. A particular challenge to modern surface interfaces is the discoverability of system functionality: does the system require gestures? are there system menus? if so, how are they invoked? This research focuses on the discoverability of system menus on digital tabletops designed for public settings. An observational study of menu invocation methods in a museum setting is reported. Study findings suggest that discernible and recognizable interface elements, such as buttons, supported by the use of animation, can effectively attract and guide the discovery of menus. Design recommendations for improving menu discoverability are also presented.