This paper describe ongoing research investigating how visualizations, especially line-graphs and charts, may be represented by haptics both to understand the structure and the values associated with the graphical realization. Much of the current research has focused mainly on the structure of the line-graph; some more recent work has used sound to depict the value of the curve. There has been limited work on multiple curves and more complex charts, with problems occurring between the crossover points of (say) a curve. We use the PHANToM Haptic interface to feel objects within the virtual world. Our investigations are focusing on a three- stage methodology: a) unguided exploration, where the user may wander and explore the haptic visualization in their own time, b) constrained navigation, where the user's point of interest is constrained to a particular path, but the user can still explore within these constraints, and c) Tours, where the user is completely guided round a predefined path.