The process of creating terrain and landscape models is important in a variety of computer graphics and visualization applications, from films and computer games, via flight simulators and landscape planning, to scientific visualization and subsurface modelling. Interestingly, the modelling techniques used in this large range of application areas have started to merge in the last years. This chapter is a report where we present two taxonomies of different modelling methods. Firstly we present a data oriented taxonomy, where we divide modelling into three different scenarios: the data-free, the sparse-data and the dense-data scenario. Then we present a workflow oriented taxonomy, where we divide modelling into the separate stages necessary for creating a geological model. We start the report by showing that the new trends in geological modelling are approaching the modelling methods that have been developed in computer graphics. We then introduce the process of geological modelling followed by our two taxonomies with descriptions and comparisons of selected methods. Finally, we discuss the challenges and trends in geological modelling.