The library, often described as the world's first major seat of learning, was said to have housed most of the works of such classical scholars as Sophocles, Plato and Socrates.
The library was burned three times in its history -- in the 1st century BC, reputedly by Julius Caesar, in 391 AD by Christians who considered the structure a house of paganism, and in 642, as ordered by the Caliph of Baghdad.
The archaeologists said they excavated parts of the Bruchion region of the Mediterranean city and discovered what look like lecture halls or auditoriums. One conspicuous feature of the rooms, they said, was a central elevated podium for the lecturer to stand on.
"It is the first time ever that such a complex of lecture halls has been uncovered on any Greco-Roman site in the whole Mediterranean area," said Zahi Hawass secretary general of Egypt's Supreme Council of Antiquities and a member of the discovery team. "It is perhaps the oldest university in the world," he added.