Mega Terrain: Oasis

Mega Terrain: Oasis is a comprehensive tool set filled with the appropriate terrains, props, and lighting presets to help you create your own desert oasis scene. You can create vast deserts, remote islands, and lush lakes with ease. The desert and oasis terrains can tile together, and be instanced out for performance purposes.

If you don't wish to create your own scenes, there are plenty of example presets to get you started.