Porth-y-Tŵr (Welsh for Tower Gate) is a gatehouse and bell tower overlooking St Davids Cathedral. It is the sole survivor of four medieval gates to the walled Cathedral Close. The 13th-century octagonal tower, adjoining the gateway, now contains the cathedral's bells.
What is nowadays the bell tower was used by the bishops of St Davids for their consistory court and a record office for the episcopal see. The south tower and the range of rooms above the gate were used as a council chamber. Well appointed apartments, suitable for the mayor, were accessed via a doorway on the town side of the tower.
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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.