Lighthouse of Alexandria
Under Ptolemy II, the city gained one of what were to become known as the seven wonders of the ancient world: the Pharos, or lighthouse at Alexandria. The approximately 350-foot-high lighthouse was an engineering wonder for its time. Situated on the island of Pharos in the city's harbor, the lighthouse was built by Sostratus of Cnidus and stood for centuries. Records indicate the lighthouse survived until the twelfth century, but by the mid-fifteenth had become so dilapidated that the Mamluke sultan Qait Bey built a fortress atop the ruins. Like the lighthouse, neither the Mouseion nor the library survived into modern times. The Mouseion complex, including the library, was destroyed by civil war under the Roman emperor Aurelian in 272; a companion library, housed in a separate complex, was destroyed by Christians in 391.