Sadd el-Kafara, an ancient earthfill dam built around 2600 BC in the Wadi Garawi, approximately 40 kilometers southeast of Cairo near the town of Helwan, is recognized as the oldest known large dam in the world. Constructed using 60,000 tons of earth and rocks, the dam measured 113 meters in length and 14 meters in width, resting on a base of 98 meters for a crest reaching 56 meters. It was built to contain sudden floods and provide water to workers and animals involved in extracting stone and marble for nearby pyramids and temples. However, it collapsed shortly after its completion due to the absence of a spillway and a diversion channel, and it never retained any water. The dam's dimensions were staggering, with an estimated storage capacity between 465,000 and 625,000 cubic meters of water. Despite its impressive size, no evidence of cultivated land has been found near the site, suggesting that the dam was not used for agricultural irrigation but rather to protect habitation areas likely located at the mouth of the wadi, where it meets the Nile valley. The upstream face of the dam was almost completed, while the downstream face remained largely underdeveloped. Its sloping crest had not been flattened or protected against overflow, leaving the structure completely defenseless against a sudden rise in water levels. The collapse of Sadd el-Kafara likely caused a catastrophic flood in the lower valley. The failure of the dam apparently discouraged Egyptian builders from undertaking similar projects for nearly eight centuries. The remaining ends of the dam are separated by a central gap of 50 to 60 meters carved by the waters thousands of years ago. Despite this breach, the remaining sides are described as being in excellent condition, a striking testimony to the initial robustness of the construction, even though it was never able to fulfill its role. Sadd el-Kafara was rediscovered in 1885 by the German archaeologist Georg Schweinfurth, less than 140 years ago. The structure has been silent for nearly 3,700 years, highlighting the degree of oblivion into which this structure had fallen despite its initial extraordinary ambition. The failure of Sadd el-Kafara is recognized as a significant event in the technical history of ancient Egypt, demonstrating that even the most advanced civilizations of their time can stumble over apparently minor details. A dam without a spillway, no matter how massive, remains vulnerable to the whims of nature.