Memphis became the capital of Ancient Egypt for over eight consecutive dynasties during the Old Kingdom. The city reached a peak of prestige under the 6th Dynasty as a centre for the worship of Ptah, the god of creation and artworks. The alabaster sphinx that guards the Temple of Ptah serves as a memorial of the city's former power and prestige.[17][18] The Memphis triad, consisting of the creator god Ptah, his consort Sekhmet, and their son Nefertem, formed the main focus of worship in the city. Memphis declined after the 18th Dynasty with the rise of Thebes and the New Kingdom but was revived under the Persians, before falling firmly into second place following the founding of Alexandria. Under the Roman Empire, Alexandria remained the most important Egyptian city. Memphis remained the second city of Egypt until the establishment of Fustat (or Fostat) in 641 CE. Afterwards it was largely abandoned and became a source of stone for the surrounding settlements. It was still an imposing set of ruins in the 12th century but soon became little more than an expanse of low ruins and scattered stone.