Sumer, or the ‘land of civilized kings’, flourished in Mesopotamia, now modern-day Iraq, around 4500 BC. Sumerians created an advanced civilization with its own system of elaborate language and writing, architecture and arts, astronomy and mathematics. Their religious system was a complex one comprised of hundreds of gods. According to the ancient texts, each Sumerian city was guarded by its own god; and while humans and gods used to live together, the humans were servants to the gods.