Calais Lighthouse is a significant landmark as well as a navigational aid to ships and ferries using the Straits of Dover. There was a beacon at the summit of the watchtower from 1818. King Louis-Philippe in his plans to improve French ports decided the construction of a first-class lighthouse in Calais. This lighthouse started operating in 1848 and was electrified in 1883. After escaping the destruction of the Second World War it was automated in 1987.
The lighthouse is 53m high, its tower is octagonal outside and round inside with walls 1,90m at the base and 1,50m at the summit. The foundations descend 7,40m under the cellars. The staircase has 271 steps leading up to the lantern. The central light of the lighthouse is permanent and the lantern, whose panels shut off the light, turns around the light, giving 4 flashes of 2/10th of a second every 15 seconds.
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.