The fundamental engineering challenge was always the same: the Red Sea appeared to sit higher than the Nile, threatening to flood Egypt's freshwater with salt. Aristotle recorded that Sesostris (likely Senusret III) had started digging a canal but abandoned the work for this reason. Darius I of Persia, who conquered Egypt around 500 BC, took up the project and -- according to his own commemorative stelae found along the Wadi Tumilat -- actually completed it. But Aristotle, Strabo, and Pliny the Elder all claimed Darius stopped short as well. The disagreement among ancient sources has never been fully resolved. What is clear is that Ptolemy II, son of Alexander the Great's general, is credited with finally solving the elevation problem around 274 BC by installing what may have been the world's first canal lock -- a gate system that kept Nile water and seawater from mixing. It was a feat of engineering that would not seem out of place in the modern era.

Each new empire that controlled Egypt rebuilt the canal to suit its own needs. Roman Emperor Trajan moved the canal's mouth on the Nile further south, to what is now Old Cairo, and renamed the waterway Amnis Traianus after himself. The entrance walls he built -- six meters thick and set 40 meters apart -- have been found beneath the present-day Coptic churches of Saint Sergius and Saint George. Emperor Diocletian later expanded the fortifications into the massive Babylon Fortress, which still stands in Old Cairo. The canal passed between two enormous round towers and through the middle of the fortress itself. When the Muslim commander Amr ibn al-As conquered Egypt in 641 AD, the canal had silted up and fallen into disrepair. He ordered it reopened, and it served again -- until the Abbasid Caliph al-Mansur sealed it in 767 AD to starve Arabian rebels of Egyptian grain.

After the canal's closure, trade between the Mediterranean and the Indian Ocean shifted to overland camel caravans running from Alexandria to Red Sea ports, or the Byzantine silk route through the Caucasus Mountains. When Portugal's Bartolomeu Dias rounded the Cape of Good Hope in 1488, the old canal's relevance seemed permanently dead. Venice, suddenly cut out of the spice trade, negotiated with Egypt's Mamluks to build a new canal, but the Ottoman conquest of Egypt in 1517 ended that plan. The Ottoman Grand Vizier Sokollu Mehmed Pasha proposed his own canal in the 1560s to counter Portuguese dominance in the Indian Ocean, but the project was canceled as too expensive. Even Napoleon Bonaparte, during his Egyptian campaign in 1799, learned of the ancient canal when his surveyor Jacques-Marie Le Pere discovered its remains. Napoleon considered rebuilding it but was dissuaded by the same erroneous belief about sea-level differences that had troubled the ancients.

After more than a millennium of silence, the connection between Mediterranean and Red Sea was finally reestablished -- but along a different path. Ferdinand de Lesseps's Suez Canal, which opened on 17 November 1869, cut directly south through the isthmus rather than following the Nile eastward through the Wadi Tumilat. The ancient route, however, has left its traces. French cartographers in the 19th century identified remnants of a north-south canal east of Lake Timsah, and Napoleon's own engineers mapped the east-west route from Bubastis to the Red Sea. Darius's commemorative stelae still mark the old canal's path through the Wadi Tumilat. The Canal of the Pharaohs is a reminder that the desire to connect two seas is not a modern ambition but one of civilization's oldest engineering dreams -- attempted, abandoned, rebuilt, and finally realized through a route that none of the ancients had tried.