It is a challenge of integrating environment, entities and human in a high fidelity virtual geographic environments (VGE), because of the complexity of the geo-phenomena, large volume of geo-spatial data, and the limitation of computer resource. We try to resolve this challenge discussed in this paper by utilizing a serious game engine, which is CryEngine, for small scale virtual environments. Methodology of CryEngine based construction of VGE is discussed. Meanwhile, several key technologies are involved, which are efficient re-construction of terrain, vehicle re-construction and dynamic simulation, human modeling and behaviors simulation, and virtual environments integration and rending respectively. A prototype of virtual campus is constructed to test the reasonability of developed methods and technologies. The result reveals that it is much reasonable to build a CryEngine based VGE to integrate environment, entities and human. The result also shows that CryEngine based VGE is of high fidelity compared with most existing virtual environments, especially for detail visualization and rendering in small scale.