This thesis is about the visualization of a Tetrahedral Irregular Network (TEN) in a web client. A tetrahedron is the simplest geometric form in 3D space, a pyramid with a triangular ground face. Its four points can lie anywhere in the 3D space as long as they do not lie on one plane. 3D objects can be composed from multiple tetrahedra. In a fully partitioned TEN even air and soil are modeled with tetrahedra. Most GIS analyses on a TEN can be deducted to an operation on the triangle simplex, therefore 3D analysis on A TEN is relatively easy compared to analysis on another 3D data structures. Chapter one (Introduction) gives an overview of the background of the research, the objectives, the requirements and the research methodology. In Chapter two (Data models for 3D geo-information) the theory around 3D data modeling is given. It starts with an explanation of the 3D feature components. In the next part, there is a comparison of 3D data representations and 3D data models and a conclusion is drawn why the TEN is the best data model. In the next paragraphs, theory on the TEN data models is given as well as theory on the derived 3D TIN and ‘TEN view’ data model. In addition, this chapter gives information how to build up a TEN dataset, about 3D topology and a comparison is made how 3D spatial (TEN) data can be stored in a database. Chapter three (Prototype related technology) gives information about XML based standards to exchange and visualize 3D and 2D data and about any other technologies that are used in the prototype made for this thesis. In Chapter four (Review of 3D GIS applications on the web) a number of 3D web GIS prototypes are discussed which have been created in the last decennium. In addition to a description of them, the prototypes are compared on a number of features and a feasibility review is done of each prototype. Some prototypes are picked out and a conclusion is made which are the best prototype examples for the development of the prototype of this thesis. In Chapter five (Prototype architecture) first the preliminary draft of the prototype is discussed. Secondly, the chapter gives a schematic overview of the realized architecture and a description of the main components and techniques of the prototype. Thirdly, the steps that have been taken over time to develop the prototype are listed. In Chapter six (Prototype components, dataset and techniques) first each component of the prototype web application is described which are a 3D view, a 2D view, a Table view, a Titlebar and an SQL box. Secondly, information is given about the datasets that have been used. Thirdly, each technique used in the prototype is explained in detail In addition some techniques that are not implemented in the prototype are discussed too. Chapter seven (Evaluation and conclusion) starts with an evaluation. First, a comparison is made which XML based language is best for 3D TEN visualization: X3D, KML, or CityGML. Secondly is reviewed in which way the data can best be stored in the database. Thirdly is compared whether it is best to visualize the TEN, 3D TIN, or TEN view. As fourth, the architecture is discussed. In the next part of Chapter six (Summary and conclusion) each sub question as stated in the Chapter one is answered. In addition, an answer is given on the main research question. Finally, remarks are made regarding feature research and recommendations.