Multi-scale navigation interfaces were originally designed to enable single users to explore large visual information spaces on desktop workstations. These interfaces can also be quite useful on tabletops. However, their adaptation to co-located multiuser contexts is not straightforward. The literature describes different interfaces, that only offer a limited subset of navigation actions. In this paper, we first identify a comprehensive set of actions to effectively support multi-scale navigation. We report on a guessability study in which we elicited user-defined gestures for triggering these actions, showing that there is no natural design solution, but that users heavily rely on the now-ubiquitous slide, pinch and turn gestures. We then propose two interface designs based on this set of three basic gestures: one involves two-hand variations on these gestures, the other combines them with widgets. A comparative study suggests that users can easily learn both, and that the gesture-based, visually-minimalist design is a viable option, that saves display space for other controls.