St. John Apostle and Evangelist (Iglesia de San Juan Apóstol y Evangelista) is a Roman Catholic Asturian pre-Romanesque church situated in Santianes de Pravia. The church contains a foundation stone in the form of a letter labyrinth ('Silo Princeps Fecit') that records the 8th-century founding of the church by King Silo of Asturias. The inscription Silo princeps fecit singularly combined in fifteen horizontal lines and nineteen perpendicular columns of letters. The T forms the beginning and the end of the first and last line in consequence of which the name Silo is not to be found till the eighth line and the S which begins it is exactly in the centre of that line and of the tenth column thus the name is in the shape of a cross as the letters above below and on each side of the S form the word Silo.
References: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.