A 26.85-metre column of red Aswan granite — the tallest single piece of polished granite anywhere in the ancient world — standing in the ruins of the great Serapeum temple complex. The Serapeum was Alexandria's principal pagan temple, and after the destruction of the main Library it housed the city's surviving scrolls in a 'daughter library' underground.
The site itself is a stripped archaeological park. The pillar dominates everything; around it lie sphinxes recovered from elsewhere in the city, the foundations of the temple, and the underground galleries of the Serapeum — sometimes called the 'sister library' — which are accessible by a stairway down. Below ground, you can see the niches that once held scrolls and the long passage that connected the library to the temple above. Entry is cheap; allow an hour. The site is a 15-minute walk from the Catacombs of Kom el-Shoqafa — combine the two.