VARIANT is an interactive system for visualizing and handling terrains with multiresolution functionalities. Terrains must have been previously encoded as a Multi-Triangulation (MT). This structure supports extraction of all possible triangulations of the terrain at variable resolution. For instance, it is possible to generate triangulations in which resolution is high just in a given region, called a focus set. A special case of a focus set is the view frustum used in perspective terrain visualization. In addition, the geometric error of the terrain representation can be customized to obey to some error threshold function. The application supplies several focus sets (circles, 2D boxes, polygonal lines, camera frustum) that can be interactivelly designed and modified on the 2D grid representing the terrain, and two types of error threshold functions (constant all over the terrain or dependant on triangle distance to viewpoint). The application also supports some computational operations on terrains. The first one is the computation of the visibility graph, i.e., of the mutual relation of visibility/invisibility for each pair of viewpoints in a given set. For such computation, we extract from the MT a triangulation that represents the terrain with a small geometric error only in the parts that are intersected by the visual ray between two viewpoints. The second computational operation is the generation of contour lines (or isolines) on a terrain. Here, the triangulation extracted from the MT has a high resolution only at the elevation corresponding to the isolines. Finally, the application supports various visualization options, and both a landscape and an exploration mode. The program is a Visual C++ application for Windows. OpenGL libraries have been used for terrain rendering.