“Beginning with Augustus, the Roman emperors took over the task of building libraries in Rome. Actually, Augustus was responsible for two public libraries. The first, in the Temple of Apollo, was begun in 36 B.C. and dedicated in 28. B.C. It was divided into two separate collections, one Greek and one Latin. Pompeius Macer was the first librarian, and Julius Hyginus, a noted grammarian, also served in that capacity. Later enlarged by the Emperors Tiberius and Caligula, this library on the Palatine Hill was one of the two major libraries in Rome for several hundred years. It was damaged at least twice by fires but survived well into the 4th century. The second Augustan library was in the Porticus Octaviae, a magnificent structure built in honor of Octavia, the Emperor’s sister. . . . Caius Melissus was the first librarian for this collection, housed in chambers over a promenade. Although damaged by fire in the reign of Titus about 80 A.D., the Octavian Library probably survived into the 2nd century“ (Harris, History of Libraries in the Western World 4th ed.  57.)
Clark, The Care of Books (1901) reproduces a plan of the Porticus Octaviae on p. 13.