Prince William and Kate, Duchess of Cambridge, visit Sept. 11 Memorial

Prince William and Kate, Duchess of Cambridge, began the third and final day of their U.S. trip with a visit to one of New York City's most somber sites -- the National Sept. 11 Memorial and Museum.

The couple walked across the memorial plaza Tuesday in pouring rain and wind, each holding a black umbrella. Wearing a fuchsia, double-breasted Mulberry coat, black tights and high heels, Kate smiled as she spoke with officials before the couple laid a bouquet of flowers at one of the reflecting pools built in the footprints of the fallen towers.

After paying their respects at the pool ringed with the chiseled names of the more than 2,700 people who died on Sept. 11, 2001, William and Kate entered the museum that commemorates the attacks.

During their half-hour visit, they descended to the bedrock level that houses exhibits.

Escorted by museum president Joe Daniels and director Alice Greenwald, the royals passed two trident-shaped columns preserved from the facade of the fallen north tower and the battered "survivors' staircase" that hundreds used to escape on 9/11.

The duke and duchess also entered the Memorial Hall, a space between the former twin towers' footprints with a wall of blue tiles representing all the 9/11 victims, plus those who died in the 1993 World Trade Center bombing. Behind the wall lies a repository of unidentified Sept. 11 remains.

The nearby "In Memoriam" exhibition has profiles of the victims. Visitors can leave a message or signature with a stylus on an electronic tablet. Kate and William both signed, writing "Catherine" and "William" in script.

Museum chief of staff Allison Blais said the duchess "talked about how in awe she was of the enormity of the space; it was something she didn't anticipate." Blais said Kate also spoke about how moving the memorial was and being able to touch the names of the victims.

About a dozen museum-goers awaited William and Kate, smartphones at the ready.

Before leaving the 9/11 site, William and Kate admired the massive, marble-clad lobby of 1 World Trade Center, graced by a large Christmas tree. The recently completed 104-floor skyscraper is the nation's tallest building.

The morning visit to the site where 67 British citizens died -- the most of any foreign country -- came on the last day of the Duke and Duchess of Cambridge's trip. Their visit to New York City and his to Washington was the first time either of them has visited those cities.

Later Tuesday evening, William and Kate are expected at a black-tie fundraiser for the University of St. Andrews, where they both got their degrees, at the Metropolitan Museum of Art.

On Monday, William went to the White House and spoke at a World Bank conference. Kate wrapped Christmas gifts and helped children decorate picture frames while touring a child development center with New York City's first lady, then talked technology, theater and more with a British-success-story guest list at a lunch at the consul general's home.

That evening, they attended a reception at the British Consul General's residence co-hosted by the Royal Foundation and the Clinton Foundation, celebrating conservation efforts, where they spent some time talking with former Secretary of State Hillary Rodham Clinton, Chelsea Clinton and her husband, Marc Mezvinsky, and later headed to the Barclays Center in Brooklyn to watch a basketball game between the Brooklyn Nets and the Cleveland Cavaliers (where they met Beyonce, Jay Z and LeBron James).