A memorial is one of the most challenging and meaningful projects an architect or designer can take on. It must be solemn but hopeful, visually impactful but respectful. Following the tragic events of September 11, 2001, many cities, both in the U.S. and abroad, have built memorials to the victims, survivors, and first responders. These symbolic designs were often years in the making, and many have faced controversy and criticism. In honor of the 16th anniversary of 9/11, AD has gathered beautifully designed tributes from New York to Italy. Conceived by some of the world’s leading architects, artists, and landscape designers, each of these moving memorials is a powerful remembrance of one of America’s darkest days.