Third Military Gate and "Sigma", Istanbul

The Third Military Gate, nestled within the historic fortifications of Constantinople, now Istanbul, serves as a testament to the city's rich military and architectural history. The Walls of Constantinople, a formidable defensive system, featured nine main gates piercing both the inner and the outer walls, alongside numerous smaller posterns. According to the classification system established by the historian Philipp Anton Dethier in 1873, these gates were divided into "Public" and "Military" categories. Public gates were named and accessible to civilians, while military gates, including the Third Military Gate, were numbered and restricted to military use.

The Third Military Gate stands as one of the two minor military gates guarding "the Sigma," a notable "C"-shaped section of the wall. This design was likely intended to enhance the defense capabilities of the wall in this specific area. Presently sealed, the gate allows visitors to witness the spot from which ancient defenders would have sallied forth to protect Constantinople. The area known as "the Sigma" continues to intrigue historians, contributing to ongoing discussions about the city's defensive strategies.

The Third Military Gate is located between towers 39 and 40. It bears the name of the quarter of the Triton ("the Third") situated behind it, indicating its significance in the city's defensive layout. The gate, which lacks a Turkish name, is attributed to middle or late Byzantine construction, highlighting its historical depth. The corresponding gate in the outer wall was intact until the early 20th century but has since vanished. It is highly probable that the Third Military Gate is synonymous with the Gate of Kalagros, merging historical records with the physical remnants of Constantinople's storied past.