The Washington Monument is an obelisk on the National Mall in Washington, D.C., built to commemorate George Washington, once commander-in-chief of the Continental Army and the first American president. Located almost due east of the Reflecting Pool and the Lincoln Memorial, the monument, made of marble, granite, and bluestone gneiss, is both the world's tallest stone structure and the world's tallest obelisk (169m).
Construction of the monument began in 1848, and was halted from 1854 to 1877 due to a lack of funds, a struggle for control over the Washington National Monument Society, and the intervention of the American Civil War. Although the stone structure was completed in 1884, internal ironwork, the knoll, and other finishing touches were not completed until 1888.
The original design was by Robert Mills, but he did not include his proposed colonnade due to a lack of funds, proceeding only with a bare obelisk. Despite many proposals to embellish the obelisk, only its original flat top was altered to a pointed marble pyramidion, in 1884. Upon completion, it became the world's tallest structure. The monument held this designation until 1889, when the Eiffel Tower was completed in Paris, France.
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.