The building was built by the Athenian philosopher Titus Flavius ​ ​ Pantaenus between 98 and 102 AD, during the reign of the Roman emperor Trajan. The library building was dedicated to Athena Archegetis along with Trajan himself and the people of Athens, according to an inscription on the lintel of the main entrance, which has survived built into the late Roman wall. The monument still exists today, but in a fragmentary state. It is partially covered by the late Roman wall of the Agora and mainly by the large tower.→