The National September 11 Memorial & Museum commemorates the September 11, 2001 attacks, which killed 2,977 people, and the 1993 World Trade Center bombing, which killed six. The memorial is located at the World Trade Center site, the former location of the Twin Towers that were destroyed during the September 11 attacks. It is operated by a non-profit institution whose mission is to raise funds for, program, and operate the memorial and museum at the World Trade Center site.
A memorial was planned in the immediate aftermath of the attacks and destruction of the World Trade Center for the victims and those involved in rescue and recovery operations. The winner of the World Trade Center Site Memorial Competition was Israeli-American architect Michael Arad of Handel Architects, a New York- and San Francisco-based firm. Arad worked with landscape-architecture firm Peter Walker and Partners on the design, creating a forest of swamp white oak trees with two square reflecting pools in the center marking where the Twin Towers stood. In August 2006, the World Trade Center Memorial Foundation and the Port Authority of New York and New Jersey began heavy construction on the memorial and museum. The design is consistent with the original master plan by Daniel Libeskind, which called for the memorial to be 9.1 m below street level, in a plaza, and was the only finalist to disregard Libeskind's requirement that the buildings overhang the footprints of the Twin Towers.
A dedication ceremony commemorating the tenth anniversary of the attacks was held at the memorial on September 11, 2011, and it opened to the public the following day. The museum was dedicated on May 15, 2014, with remarks from then mayor of New York City Michael Bloomberg and then President Barack Obama.
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.