It was located at the southeast end of the Agora of Athens, south of the Stoa of Attalus, on the left side of Panathenaion Street.

The library building was dedicated to Athena Archegetis,[3] with Trajan himself and the people of Athens, according to an inscription on the lintel of the main entrance, which is preserved embedded in the late Roman wall,.

One was a large open courtyard measuring 20 × 13.5 m, the floor of which was paved with small irregular marble tiles embedded in mortar.

[6][7][5] ΑΘΗΝΑ ΠΟΛΙΑΔΙ ΚΑΙ ΑΥΤΟΚΡΑΤΟΡΙ ΚΑΙΣΑΡΙ ΣΕΒΑ{Σ}ΣΤΩ ΝΕΡΒΑ ΤΡΑΪΑΝΩ ΓΕΡΜΑΝΙΚΩ ΚΑΙ ΤΗ ΠΟΛΙ ΤΗ ǀ ΑΘΗΝΑΙΩΝ Ο ΙΕΡΕΥΣ ΜΟΥΣΩΝ ΦΙΛΟΣΟΦΩΝ Τ. ΦΛΑΒΙΟΣ ΠΑΝΤΑΙΝΟΣ ΦΛΑΒΙΟΥ ΜΕΝΑΝΔΡΟΥ ΔΙΑΔΟΧΟΥ ǀ ΥΙΟΣ ΤΑΣ ΕΞΩ ΣΤΟΑΣ ΤΟ ΠΕΡΙΣΤΥΛΟΝ ΤΗΝ ΒΥΒΛΙΟΘΗΚΗΝ ΜΕΤΑ ΤΩΝ ΒΥΒΛΙΩΝ ΤΟΝ ΕΝ ΑΥΤΟΙΣ ΠΑΝΤΑ ǀ ΚΟΣΜΟΝ ΕΚ ΤΩΝ ΙΔΙΩΝ ΜΕΤΑ ΤΩΝ ΤΕΚΝΩΝ ΦΛΑΒΙΟΥ ΜΕΝΑΝΔΡΟΥ ΚΑΙ ΦΛΑΒΙΑΣ ΣΕΚΟΥΝΔΙΛΛΗΣ ΑΝΕΘΗΚΕ Transcription « Ἀθηνᾷ Πολιάδι καὶ Αὐτοκράτορι Καίσαρι Σεβα{σ}στῷ Νέρβᾳ Τραϊανῷ Γερμανικῷ καὶ τῇ πόλι τῇ ǀ Ἀθηναίων ὁ ἱερεὺς Μουσῶν φιλοσόφων Τ. Φλάβιος Πάνταινος Φλαβίου Μενάνδρου διαδόχου ǀ υἱὸς τὰς ἔξω στοάς, τὸ περίστυλον, τὴν βυβλιοθήκην μετὰ τῶν βυβλίων, τὸν ἐν αὐτοῖς πάντα ǀ κόσμον, ἐκ τῶν ἰδίων μετὰ τῶν τέκνων Φλαβίου Μενάνδρου καὶ Φλαβίας Σεκουνδίλλης ἀνέθηκε »Translation To Athena Polias and to the Emperor Caesar Augustus Nerva Traianus Germanicus[8] as well as to the city of Athens, the priest of the Muses of philosophers, T. Flavius Pantainos, son of the Flavius Menander the Successor, dedicated at his own expense the outer galleries, the peristyle, the library with the books and all the ornaments contained therein, with his children Flavius Menander and Flavia Secundilla.White marble plaque - Found in the ancient Agora of Athens.

ΑΝΥΓΗ ΣΕΤΑΙ ΑΠΟ ΩΡΑΣ ΠΡΩ ΤΗΣ ΜΕΧΡΙ ΕΚΤΗΣ Transcription «Βυβλίον οὐκ ἐξενεχθήσεται, ἐπεὶ ὠμόσαμεν· ἀνυγήσεται ἀπὸ ὥρας πρώτης μέχρι ἕκτης.»Translation No book shall be taken out, since we have sworn it.