Ithomi was the strongest natural and artificial fortress in Messenia, controlling the Stenyclarus Valley to the north and the Makaria Valley to the south. Strabo compares it, in terms of strategic importance, to Corinth. “Whoever conquered the two cities ruled the Peloponnese. Whoever held the two horns (Ithome and Acrocorinth) ruled the mountain,” as the Megalopolitan historian Polybius aptly observes (3.19, 9–11).

The outer wall of Messene was built with stone corbels up to the battlements without the use of rubble masonry for the superstructure, as was generally the custom in the construction of ancient fortifications: “I have not seen the walls of the Babylonians or the Memnon Colossi at Susa in Persia, nor have I heard of them from eyewitnesses; but of the walls of Ambrossus in Phocis, Byzantium, and Rhodes— cities that were excellently fortified—the walls of the Messenians are the strongest,” notes the traveler Pausanias with admiration (4.31, 4–6).

The wall of Messene is best preserved on the north-northwest side of the enclosure, on either side of the Arcadian Gate. Based on the surviving traces, its course can be precisely determined over a length of 9.5 km. Large rectangular limestone blocks were used, quarried on site from the rocky massif of Ithomi, where many locations with traces of quarrying remain, as well as on the opposite mountain of Eva (present-day Agios Vasilios). The summit of Ithomi was also fortified, where the acropolis and the sanctuary of Zeus Ithomatas were located near the now-abandoned old Vulcano Monastery with its main church dedicated to Panagia Vulkaniotissa. The towers are generally square, with the exception of one horseshoe-shaped tower and one with a circular plan.

The eastern Laconic Gate, also known as the Tegean Gate, no longer survives. It was destroyed during the construction of a road from the village to the new Voulkano Monastery as early as the 18th century. Embedded in the inner northeast corner of the monastery’s enclosure are a relief of Artemis and the lower legs of a marble male statue, fused with a brick. The western gate, the Arcadian Gate, is fairly well-preserved and has been the city’s hallmark since the time of the earliest travelers, who repeatedly depicted it in their engravings. It is a structure of monumental proportions, built with massive limestone blocks that inspire awe. It was in better condition when it was surveyed in 1828 by the French Mission of Moreau.  It is circular on the inside, with a spacious interior 21 m in diameter, and features two entrances: a simple exterior entrance without a door, and an inner double entrance that led to a street heading toward the city’s marketplace. In the inner circular space, there is one niche to the right and one to the left of the entrance, where Hermetic columns once stood. Pausanias, leaving the city of Messene through the Arcadian Gate and heading toward the bridge over the Balura River (note: Mavrozoumenas) and the northern Messinian plain of Stenyklaros, saw the Herm columns in their places and described them as works of Attic art (4.33, 3). Two square towers with guard quarters on the upper floor protected the outer entrance on the right and left. An impressive monolithic central lintel (now leaning at an angle and broken in two) divided the entrance into two gateways with deeply carved chariot-wheel grooves in their stone thresholds. In the southwestern section of the fortification, there was a pointed opening in the thickness of the wall that served as a stream bridge. It was in good condition when it was surveyed in 1828 by members of the French Mission to Morea.