To make your own neighborhood, you'll need "SimCity 4." To make a custom terrain for "The Sims 2," make a new small (64x64) city in "SimCity 4." Here you have almost free reign of how you design the area. You can use mountains, rivers, canyons, and the other terrain tools. What you must not do is use other bridges other than the default, and diagonal roads, only use straight roads.
How to Make Terrain for "The Sims 2"
- Create a small city in "SimCity 4" or "SimCity 4 Deluxe."
- Customize the city with mountains, rivers, and other terrain modifications.
- Save your city and exit when you are finished.
- Open Windows Explorer.
- Go to: C:\Program Files\Maxis\SimCity 4 Deluxe\Regions\ and find the city you just created.
- Copy the .sc4 file to: C:\Documents and Settings\[User]\My Documents\EA Games\The Sims 2\SC4Terrains
- Next time you start a new neighborhood, your terrain will be listed in "The Sims 2."

