The Church of San Xoán (or Saint John) of Portomarín is an unusual Late Romanesque temple as it is designed to be both a church and a castle and so has architectural characteristics of both buildings. As a church it has one barrel vaulted nave, a semicircular apse and all the typical decorations of Romanesque churches; these include a carved portal with archivolts, rose windows and carved capitals. As a castle its perimeter is surrounded by merlons, it has four defense towers (one at each corner) while behind it lies an adarve, a defensive street. The north west tower currently has a stork's nest with two young (2011). The church was relocated to its current position from the valley in the 1960s when the river was flooded to form a reservoir.
It is situated on the principal route of the Way of St. James to Santiago de Compostela, where other Templar and Knight Hospitaller churches and castles were constructed as a result of the effort of the Hospital Orders to protect the way to the tomb of Santiago; others include the churches of Torres del Río, Eunate and the Castle of Ponferrada.
The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.