A dedication ceremony took place at the World Trade Center site yesterday, marking the completion of the National September 11 Memorial Museum before it opens to the general public on May 21. President Obama was in attendance for the ceremony, which honored those killed in both the terrorist attacks of September 11, 2001, and the earlier February 26, 1993 bombing.

The museum comprises two sections: a large pavilion, and the Memorial Museum proper, which lies beneath. Norwegian architecture firm Snøhetta was handed the difficult task of designing the pavilion – the sole visible building in the immediate vicinity – and all visitors must first pass through it before gaining access to the subterranean Memorial Museum.

The pavilion features three floors and resembles a partly-damaged tower, with a reflective and striped facade. It has a LEED Gold rating and features sustainable technology including energy-efficient lighting, energy management systems, and wastewater recycling. The pavilion's poignant interior decor includes two salvaged columns from the original twin towers.

NYC architects Davis Brody Bond designed the underground museum, which is accessed by descending a gentle slope within the pavilion. The museum contains artifacts pertaining to the September 11 attacks, in addition to exhibitions which tell the wider story of the World Trade Center, the Pentagon, and Flight 93.

"The opening of the 9/11 Museum is an important milestone for our city and our country," said Michael R. Bloomberg, chairman of the 9/11 Memorial and Museum, and former Mayor of New York City.

"The Museum tells heartbreaking stories of unimaginable loss, but also inspiring stories of courage and compassion. Its opening honors the commitment we made to 9/11 family members and to all future generations: That we would never forget those we lost or the terrible lessons we learned that day. So many people from across the country and around the world made the Museum possible – including New York City school children who donated their pennies – and they all have my deepest gratitude."

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