The Sphinx has some of the least restrictive placement requirements of any improvement - any passable land tile is fair game, except for Snow and Snow Hills in Gathering Storm. The Egyptians should build them on tiles that can't support other improvements, or adjacent to wonders for some extra Faith. Thanks to their Appeal bonus, well-placed Sphinxes can create good spots for Seaside Resorts and National Parks, or increase the yields of those that are already there.
Civilopedia entry Edit
In contrast to the Greek version, the Egyptian sphinx has a human head on a lion’s body, is benevolent, and is the guardian of temples and tombs. Perhaps the first Egyptian sphinx constructed was during the Fourth Dynasty (c. 2500 BC) that depicted the face of Queen Hetepheres II, daughter of famed Khufu. But the sphinx was a common motif among those eternity-obsessed pharaohs; other famous ones include that depicting Hatshepsut and the “alabaster sphinx” of Memphis. Then there is that “Great Sphinx” at Giza that bears the likeness of the pharaoh Khafra (who is otherwise historically insignificant). Smaller ones lined the approaches to tombs and temples, and any number were put at the top of stairways in palaces and public places. By the 18th Dynasty, one could hardly swing a cat in Egypt without hitting a sphinx.