In this study, a knowledge management based Decision Support System has been suggested. By collecting the data of people, event and properties of building, a 3D navigation system has been developed to support building management and users during the extraordinary circumtances. Most of the current navigation systems are still in the 2D environment and that is insufficient to visualize 3D objects and to obtain satisfactory solutions for the 3D environment. Therefore, there is currently still a lack of implementation of 3D network analysis and navigation for indoor spaces in respect to evacuation. 3D navigation within a 3D-GIS environment (Three Dimensional Geographical Information Systems) is increasingly getting more popular and spreading to various fields. In the last decade, especially after the 9/11 disaster; evacuating the complex and tall buildings of today in case of emergency has been an important research area for scientists. The objective of this paper is to implement 3D visualization and navigation techniques and solutions for indoor spaces within 3D-GIS. For realizing this, we have proposed a GIS implementation that is capable of carrying out 3D visualization of a building model stored in the CityGML format and perform analysis on a network model stored in Oracle Spatial. The proposed GUI also provides routing simulation on the calculated shortest paths with voice commands and visual instructions.