Byzantine fortifications were military structures built by the Byzantine Empire to protect cities and strategic locations. These fortifications often included thick walls, towers, and gates, designed to withstand attacks from enemies. The use of advanced engineering techniques allowed for the construction of formidable defenses, which were crucial for the empire's survival. Key examples of Byzantine fortifications can be found in cities like Constantinople and Thessaloniki. The walls of Constantinople, in particular, were renowned for their strength and complexity, featuring multiple layers and a series of defensive towers. These fortifications played a vital role in the empire's ability to defend against invasions for centuries.