The city of Eridu is the oldest city in the world, not approximately the oldest, not among the oldest, the oldest. The archaeological evidence is unambiguous on this point. The site known today as Tell Abu Shahrain in southern Iraq contains occupation layers dating to approximately 5400 BCE, making Eridu older than Ur, older than Uruk, older than every other urban site yet discovered anywhere on Earth.
The Sumerians themselves knew this. The Sumerian King List, one of the most studied documents in ancient history, preserved in multiple copies from multiple cities, opens with a declaration that has been translated thousands of times and is still debated by scholars today. After kingship descended from heaven, kingship was in Eridu, not in Ur, not in Nippur, not in Shuruppak, Eridu.
The first city, the first kingship. The first place where something the Sumerians recognized as organized human civilization existed on Earth. And then Eridu was abandoned. Not conquered, not destroyed, not buried by flood or burned by invaders, abandoned. The archaeological record at Tell Abu Shahrain shows occupation layers building continuously from approximately 5400 BCE through the early 3rd millennium BCE, nearly 2500 years of unbroken habitation, the longest continuous urban occupation in human history. And then the occupation stops.
The layers simply end. The city that the Sumerians themselves described as the foundation of human civilization, the city of Enki, the city where the Me were kept, the city that the Eridu Genesis names as the first settlement established by the gods before the flood, was empty by approximately 2050 BCE, not gradually depopulated over centuries.
The archaeological evidence shows a functioning urban center and then an absence. Now, let’s establish what Eridu actually was before we address why it was abandoned. Because Eridu is not simply the oldest city, it is the oldest city with a continuous temple sequence that tells us something extraordinary about the people who built it and what they believed they were doing there.
Beneath the great ziggurat of Eridu, the massive mud-brick temple platform that stands today as the most visible feature of the ancient site, archaeologists excavating in the 1940s and 1950s under the direction of Fuad Safar and Seton Lloyd found something that stopped them. Beneath the ziggurat they found an earlier temple.
Beneath that earlier temple they found another. Beneath that one another. 18 successive temples built one on top of the previous, each in exactly the same location, each oriented in exactly the same direction, each following the same basic architectural plan with variations in scale and elaboration across the millennia. 18 temples spanning the entire occupation period of the city from the earliest Ubaid period levels at the bottom to the late 3rd millennium levels at the top, the same sacred space maintained continuously for 2,500 years. This is
not what you find at other ancient sites. At other Mesopotamian sites the temples move. They are rebuilt in new locations, reoriented, expanded in different directions as cities grow and change. The sacred geography of most ancient urban centers shifts across time. At Eridu it did not shift.
The sacred space was fixed and every generation of the city’s inhabitants for 2,500 years built their temple in exactly the same place facing exactly the same direction over the remains of what their predecessors had built. The consistency across 18 successive temples spanning 2,500 years suggests that whatever was being honored at Eridu was not a religious convention that shifted with political change or theological development.
It was a fixed location, something specific about the place itself. The Sumerian texts are explicit about what that something was. Eridu was the home of the Abzu. The Abzu, sometimes transliterated as Apsu, is described in Sumerian and Akkadian literature as the underground freshwater ocean that lies beneath the earth.
In the religious literature, it is the domain of Enki, the god of wisdom and practical knowledge. It is the source of all freshwater. It is the place where the Me, the fundamental divine laws and principles that govern civilization, are kept. Enki’s house at Eridu sits above the Abzu. The temple is the meeting point between the surface world and the underground freshwater realm below.
This is consistent with the physical geography of the site. Eridu sits at the edge of what was once a freshwater lagoon, the Hammar Marsh system, that in the ancient period extended significantly further north and west than it does today. The water table at Eridu is high. In the ancient period, freshwater would have been accessible at shallow depth directly beneath the temple precinct.
The Abzu was not purely mythological. There was freshwater beneath Eridu. The 18 successive temples were built above it for 2,500 years, and then the city was abandoned. Now, let’s address what the archaeology actually shows. The excavations conducted by Safar and Lloyd in the late 1940s produced detailed stratigraphic records of the Eridu sequence.
Their work remains the foundation of everything we know about the site’s physical history. What the stratigraphy shows in the final occupation levels is this. The city did not show signs of destruction, no burning layers of the kind that mark military conquest, no collapsed architecture consistent with earthquake damage, no flood deposits of the kind that appear at sites devastated by river inundation.
What the final occupation layers show is a city in use followed by a city not in use. The transition between these two states in the archaeological record is abrupt enough that the excavators themselves noted it. The material culture of the final occupation period. The pottery, the tools, the administrative objects is consistent with a functioning urban center, and then it is absent.
The most significant detail in the final occupation record is the temple. The 18th and final temple in the sequence was not completed. It was begun. The foundation courses were laid. The walls were partially raised. The basic structure of the building was underway, and then the construction stopped. The half-finished temple was never completed.
The workers who were building it did not return. The city that had maintained the same sacred space continuously for 2,500 years left its final temple unfinished. This is not the pattern of a city that was gradually abandoned as its population migrated to more prosperous urban centers, a process that archaeological sites show as a long tail of decreasing material culture, reduced occupation density, declining building maintenance.
This is the pattern of a city that was functioning and then stopped functioning quickly. Now, let’s address the explanations that have been proposed. The most widely cited explanation in the academic literature is environmental, specifically the progressive salinization and desiccation of the southern Mesopotamian environment during the late 3rd millennium BCE.
This is a real and well-documented phenomenon. The agricultural system of ancient Mesopotamia depended on irrigation, and sustained irrigation in an arid environment progressively increases the salt content of the soil as evaporation deposits mineral salts left behind by the receding water. Over centuries, heavily irrigated agricultural land becomes less productive as salinity rises.
This process, called secondary salinization, is documented in the archaeological and paleoecological record across southern Mesopotamia and is widely accepted as a contributing factor in the decline of several Sumerian cities. The explanation has real merit for understanding the broader decline of Sumerian urban civilization in the late 3rd millennium.
It has significant problems as an explanation for Eridu specifically. The first problem is the abruptness. Secondary salinization is a process that unfolds over generations. Its effects on agricultural productivity would have been felt gradually, producing the long-tail abandonment pattern that the Eridu record does not show.
The second problem is the timing. Eridu’s abandonment occurs around 2050 BCE, but the city of Ur, located approximately 24 km from Eridu, continues as a major urban center for centuries after Eridu’s abandonment. The 3rd Dynasty of Ur, one of the most prosperous periods in Sumerian history, is dated to approximately 2112 to 2004 BCE.
Ur was flourishing in the same period and the same environment that supposedly made Eridu uninhabitable. If the environmental conditions that drove Eridu’s abandonment were regional, Ur should have been affected simultaneously. The third problem is the water. Eridu’s reason for existing, the feature that made it significant, the feature that 18 successive temple-building generations were honoring, was the freshwater source beneath it.
A freshwater source in an arid environment does not become less valuable as the environment becomes more arid. It becomes more valuable. If anything, environmental pressure should have made Eridu more important, not less. The salinization explanation does not adequately account for the specific abandonment of Eridu at the specific time it was abandoned.
The second major explanation involves political economy, the shift of Sumerian political and economic power northward and the emergence of Akkadian dominance under Sargon of Akkad around 2334 BCE. This explanation has its own problems. Political and economic marginalization typically produces gradual urban decline, not abrupt cessation.
Cities that lose political importance become smaller and poorer over time, not empty overnight. The archaeological record of Ur shows exactly this pattern in its own later decline. A long drawn-out reduction in occupation over centuries. Eridu does not show this pattern, and Eridu was not simply politically marginal. It was religiously central.
The Sumerians continued to regard Eridu as the most sacred city in the world long after it was abandoned. Ur-Nammu, the founder of the third dynasty of Ur, conducted restoration work at Eridu after its abandonment. He rebuilt the ziggurat and restored the temple precinct. He treated the empty city as a sacred site worth maintaining even without a resident population.
The political economy explanation struggles to account for a city that retained immense religious significance being left physically empty. The third explanation, less often stated explicitly but present in the archaeological literature as an acknowledged gap, is essentially that we do not know. The 2002 survey work at Tell Abu Shahrain, conducted by an Iraqi-Italian team, produced updated ceramic sequences and stratigraphic data that refined the picture of the site’s final occupation period without resolving the question of why it
ended when it did and how quickly. The honest state of the archaeological literature on Eridu’s abandonment is that the proposed explanations are inadequate and that the question remains genuinely open. Now, let’s address what the Sumerian texts say about Eridu because the physical archaeology does not exist in isolation.
It exists alongside a body of ancient literature that describes Eridu in ways that are worth taking seriously as historical testimony, even when they resist straightforward interpretation. The Eridu Genesis, one of the oldest Sumerian literary texts, preserved on a tablet in the the collection at the University of Pennsylvania Museum describes the creation of humanity and the establishment of the first cities.
It names Eridu as the first city established. It describes the me, the divine principles of civilization, as kept at Eridu in Enki’s temple above the Abzu. The text is fragmentary. Large sections are missing. What survives describes a world in which the gods established civilization at Eridu. And then, following [snorts] the flood, that civilization was redistributed across multiple cities.
The Lamentation over the destruction of Sumer and Ur, a well-studied Sumerian literary text describing the collapse of the third dynasty of Ur, contains passages that refer to Eridu in ways that scholars have consistently described as puzzling. The Lamentation describes Eridu as abandoned before the events it is lamenting.
Eridu is already empty when the third dynasty of Ur falls, and the Lamentation’s description of Eridu’s emptiness uses language that is different from its description of the other cities destroyed in the political collapse it is mourning. The other cities are described as destroyed, attacked, conquered, mourned. Eridu is described using a compound Sumerian term that translates most directly as return to the deep, a phrase that the text’s editors have consistently interpreted as a metaphor for divine abandonment. Return
to the deep. The city above the Abzu returned to the Abzu. This is the standard mythological interpretation, but the phrase return to the deep also has a literal reading. The freshwater lagoon and marsh system that made Eridu’s location significant was dynamic in the ancient period. The shoreline of the Hammar Marsh moved.
The level of the water table shifted with climate variation. In the period around 2050 BCE, there is paleoecological evidence from sediment cores in the southern Mesopotamian region suggesting a significant rise in groundwater levels associated with a broader regional hydrological event. The Abzu, the freshwater source beneath Eridu that 10,500 years of temple building had honored, may have literally risen, not metaphorically returned to the deep.
The deep may have returned to it. A rising water table that submerged the lower city levels, contaminated the freshwater sources, and made the ancient site physically untenable for occupation. This is not an established explanation in the academic literature. It is an inference from the convergence of the paleoecological data and the literal reading of the Sumerian textual evidence, but it is consistent with the abruptness of the abandonment.
It is consistent with the unfinished temple. Construction stopped not because the builders chose to leave, but because the ground beneath them was changing. It is consistent with the phrase return to the deep, and it is consistent with the one detail about Eridu’s abandonment that is most often overlooked in the academic discussions. Eridu was not demolished.
When a city is abandoned gradually, its buildings are systematically dismantled and the materials reused. The organized removal of architectural materials, roof beams, fired bricks, stone threshold blocks, is one of the most consistent signatures of planned abandonment in the archaeological record.
At Eridu, the buildings are not systematically dismantled. They are simply there, standing, or having collapsed in place over the centuries since they were left standing. The people who left Eridu did not take the city apart before they went. They left what they had built, including the unfinished temple, and the Sumerians who came after them, the builders of the Third Dynasty of Ur, the authors of the great literary texts, the inheritors of the civilization that Eridu had started, continued to regard the empty city as the most sacred place in the world. They
sent workers to maintain it. They composed lamentations about it. They named it first in every list of ancient cities. They kept describing it as the place where kingship descended from heaven and civilization began. They kept saying that Enki’s house was there, above the Abzu, above the deep, toward which the lamentation says Eridu returned.
The 18th temple was never finished. The workers left. The city emptied. The deep came back. And the oldest city in the world has been uninhabited for 4,000 years. Archaeology knows what happened. I do not know why. The unfinished walls are still there. The water table beneath the site is still high.
The 18 temples are still stacked beneath the ziggurat, one on top of the other, each one exactly where the previous one was, exactly oriented the same way, across 2,500 years of people who agreed about something so completely that not one of them ever moved the sacred space 1 m in any direction. The oldest city in the world, the first place kingship came down from heaven, left unfinished in a hurry, with everything still inside.
