The United States' Future Combat Systems (FCS) includes a wide variety of military platforms, which will help soldiers in conflicts of the 21^st century, including: manned and unmanned, ground and air, sensors and weapons capabilities. FCS includes the Objective Force Warrior (OFW) combatants and various unmanned sensors, which operate within close-in environments requiring a high level of detail in the Synthetic Natural Environment (SNE). This paper describes the development of a set of correlated Semi-Automated Forces (SAF) and visual SNE for FCS experiments. The development and significant features of three SNEs are discussed. The first SNE is an urban database that contains a large number of Multiple Elevation Structure (MES) buildings (with interiors). The challenges associated with this quantity of MESs along with the implemented solution are discussed. The second SNE discussed is a mountain database that contains complex cave structures with different types of ground access, and tunnel geometries. The challenges with the junction of the terrain skin and tunnel access along with various solutions are discussed. The third SNE is a complex and dense jungle database with restricted mobility and line-of-sight. The challenges with modeling a jungle SNE that permits warfare along with the implemented solutions are discussed.