What are the natural barriers of the ancient sumerians

Ancient Egypt was protected from other civilizations by these natural boundaries, but that does not mean they had no contact with other civilizations. Egyptians traded with several of their contemporaries, especially the Greeks. Nevertheless, their relative isolation allowed their culture to develop uniquely.
Egyptians benefited greatly from their geography. In addition to the protection afforded by the nearby mountains, seas and deserts, they were able to develop an agrarian culture thanks to the annual flooding of the Nile River. Each year, the river would swell and eventually overrun its banks, flooding vast areas of flat ground near the river. When the waters receded, the soil was fertile and full of moisture. The combination of the flood-enriched soil and nearly constant warmth and sunshine allowed the region to farm crops successfully.

The answer would be limited.