9/11 Museum opens

Cards and mementos of those who died at Ground Zero on September 11, 2001, are a tiny part of the many heart-wrenching personal items, photos, burnt and twisted vehicles on display at the new National September 11 Memorial & Museum in New York.

The museum houses more than 10,000 artifacts and was built where the Twin Towers once stood near a permanent memorial that opened three years ago. It opens to the general public on May 21, and will be open to victims' families, survivors, first responders, workers, and local residents for a six-day dedication period beforehand.

The salvaged girders from the World Trade Center rise into the museum's airy entrance pavilion. The rest of the impressive museum space is below ground, with ramps that lead visitors on an emotional journey that retraces the tragedy.

Photographs and videos document the events of that day, showing images of the towers collapsing and people falling from them. Voices heard in a darkened room express the shock and horror.

What is left of a television and radio antenna from the North Tower bears testimony to the brutality of the suicide attack on that fateful day almost 13 years ago.

Heartbreaking items, like the dust-covered shoes of those who fled the skyscrapers' collapse, are arranged in display cases.

A firetruck with a twisted ladder commemorates the sacrifices of 343 firefighters who died in the deluge of fire and steel that accompanied the towers' collapse.

Dark corridors are filled with the voices of people remembering the chaos of 9/11 as visitors walk past the battered "survivors' staircase" from a nearby street that hundreds used to escape the burning towers.

The visit ends in a room where a video explains the rise of al-Qaeda. Some critics have expressed concern it could lead museum visitors to associate the terrorist group with Islam in general.

President Barack Obama and a group of survivors and victims' families marked the opening of the museum. Obama is mindful of "the need to remember and the power of memory in a nation's history, as well as the need to properly grieve and rebuild," White House spokesman Jay Carney said.