The Abbasid institution known as Bayt al-Hikma, tied in popular memory to a grand state academy of translators in ninth-century Baghdad — but which careful scholarship suggests was most likely a far more modest caliphal palace library and translation bureau, possibly tied especially to Persian administrative and astrological material. The entry is an anatomy of how a real but smaller institution becomes a civilizational myth, and why the smaller truth may be the more impressive one.
A modern textbook will tell you the House of Wisdom was a great academy in Baghdad, with halls of salaried scholars turning the wisdom of dead Greeks into Arabic, a rival to ancient Alexandria. Video games and documentaries draw it as a domed palace of learning, and its supposed destruction by the Mongols is mourned as a wound to the human mind. Almost none of this rests on solid evidence. What the sources actually attest is a caliphal library, and the gap between that library and the legend is one of the most instructive things a curious person can study: a case of how a civilization's genuine achievement gets compressed by later memory into a single mythic building.