This library is one of the most beautiful structures in Ephesus.. It was a monumental tomb for Gaius Julius Celsus Polemaeanus, the governor of the province of Asia from his son Galius Julius Aquila built in 117 A.D. It may be that Celsus was granted heroic honors, which would furthur justify the expense. The grave of Celsus was beneath the ground floor, across the entrance and there was a statue of Athena over it, as the goddess Athena was the goddess of the wisdom.

The scrolls of the manuscripts were kept in cupboards in niches on the walls. There were double walls behind the bookcases to prevent them from the influence of temperature and humidity. The capacity of the library was more than 12,000 scrolls, thus it was the third richest library in ancient times after the Alexandra and Pergamum.

The Library of Celsus is 21m wide and over 16m high with a 2.4m-deep portico. The facade of the library has two-stories, columns with Corinthian style on the ground floor and three entrances to the building. There is three windows openings in the upper story. They used an optical trick that the columns at the sides of the facade are shorter than those at the center, giving the illusion of the building being greater in size.

The statues in the niches of the columns today are the copies of the originals. The statues symbolize wisdom (Sophia), knowledge (Episteme), intelligence (Ennoia) and valor (Arete). These are the virtues of Celsus. The library was restored with the aid of the Austrian Archaeological Institute and the originals of the statues were taken to Ephesus Museum in Vienna in 1910.

There was an auditorium, which was used for lectures or presentations between the library and the Marble Road, built during the reign of the Emperor Hadrian.

Some centuries later after its construction a fire destroyed the reading room and the library fell into disuse. The facade collapsed in an earthquake in the 10th century.
The Library of Celsus was raised from the ruins to its present splendid state by F. Hueber of the Austrian Archaeological Institute between 1970 and 1978.