On the 20th anniversary of 9/11, “Sunday Morning” visits Lower Manhattan, and the memorial to those who were lost. Videographer: Derek Davis.

In January 2004, the design submitted by architect Michael Arad and landscape architect Peter Walker, Reflecting Absence, was chosen as the winning entry. Their design features twin waterfall pools surrounded by bronze parapets that list the names of the victims of the 9/11 attacks and the 1993 World Trade Center bombing. The pools are set within a plaza where more than 400 swamp white oak trees grow.

The Memorial opened on September 11, 2011, 10 years after the 9/11 attacks.