Tell el-Maskhuta is in northeast of Cairo, along the Ismailia Canal.
In the 1800s the existence of a large quadrangular walled city was already known but had never been well-documented.
The wall was already partially visible "just for a brief stretch" at the beginning of the excavation, according to Giuseppina Capriotti Vittozzi, manager of the Italian Archaeological Centre in Cairo.
The excavation titled 'Multidisciplinary Egyptological Mission' is being conducted by CNR's Institute of Ancient Mediterranean Studies, which has been working at the site for some years with the cooperation of the Institute for Applied Technologies in Cultural Heritage represented by Andrea Angelini.
Vittozzi said in November "an enormous wall, 22 metres long and eight metres high" was found.
"It connects to the square fortress with two 12-metre-long walls," she said.
She said those walls were just discovered as well, and "they constitute a different defensive structure of gigantic proportions".
The site is in "Wadi Tumilat", a valley that was "a very ancient route connecting Egypt and the Levant, between the land of the pharaohs and Palestine, Syria, up to Mesopotamia," Vittozzi said.
She said the area has been a place of commercial and cultural exchange since ancient times.
At the site there are also traces of a settlement of Hyksos, foreigners who dominated part of Egypt more than 3,500 years ago; this is the settlement upon which the successive fortress is situated.
A study of ceramics found at the site, led by Maria Cristina Guidotti who heads the Egypt section of Florence's Archaeological Museum, suggests that the revealed structure was added to the previous one in the Ptolemaic era (3rd-1st century B.C.).
"The great complex, as it is known now, measures about 200 by 300 metres," Vittozzi said, relying on the opinion of Mohamed Abdel-Maksoud, an Egyptian archaeologist who is part of the CNR team and is specialised in fortresses.
The fortress makes up the part of the city whose ruins are still hidden by a dune measuring nearly one kilometre and running alongside the Ismailia Canal, known in ancient times as Tjekw, and known today as Tell el-Maskhuta.
The agglomerate worked as a "filter" for the Canal of the Pharaohs, which in ancient times served the same function that today's Suez Canal serves, connecting the Mediterranean and the Red Sea.
From the beginning, investigations at Tell el-Maskhuta were made using advanced technologies, including satellite remote sensing conducted with Cosmo-SkyMed data from the Italian Space Agency (ASI) and geophysical prospecting conducted by a team from the University of Molise led by Marilena Cozzolino.
(ANSAmed).