Custom neighborhoods are made with Sim City 4. If you'd like to make your own, there are instructions here: Creating Custom Neighborhoods

Each neighborhood zip file includes the .sc4 file, and 5 .png files. The .png files include one for the picture that appears in the Create Custom Neighborhood screen, and one for each of the different terrain types (lush/temperate, desert, dirt, concrete) to appear on the Neighborhood Selection screen.

Unzip the files into your My Documents\EA Games\The Sims 2\SC4Terrains folder if you chose a standard installation location.

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