Portara (Main Gate) and Byzantine Walls of Thessaloniki, Thessaloniki

The Walls of Thessaloniki used to encircle the city from the Middle Ages until 1874 when much of them, especially the parts facing the sea, were destroyed during Ottoman renovations of Thessaloniki.

The remaining section of the Walls dates back to around 390 AD, built during the early Byzantine period, with some parts originating from an earlier construction in the late 3rd century. They're made of the typical late Roman style with alternating layers of stone and brick.

Today, the Walls stretch about 4 kilometers, half of their original length of 8 kilometers, and stand up to 10-12 meters tall and 4.5 meters wide. On the northeast side, they climb up the hills and connect with the Acropolis and Heptapyrgion Fortress.

In 1355, Byzantine Empress Anna Palaiologina modified some parts of the Walls, creating two gates known as Doors to the Walls, and another one to the west called "Portara," meaning Great Gate. These gates provided safe passage for citizens to seek refuge in the Acropolis and Heptapyrgion during attacks or sieges.

The Portara, the main gate, is well-preserved, showing layers of brickwork from repairs done over the centuries. The Walls also feature around 50 towers, including some from the Byzantine era like Klaudianos, Relief, Ormisda, and Andronikos Lapardas towers, as well as those from the Ottoman period such as the White Tower and the Chain/Triangle Tower. The Walls of Thessaloniki are recognized as a UNESCO World Heritage Site.