1. Its MissionThe exhibits tell the stories of the nearly 3,000 people killed in the 2001 attacks and the 1993 World Trade Center bombing, as well as those of survivors and first responders. Museum Director Alice Greenwald said the museum is "about understanding our shared humanity," while former mayor Michael Bloomberg called it a reminder "that freedom is not free."
Carolyn Kaster / AP
2. The Museum's SizeThe museum occupies 110,000 square feet on the 16-acre trade center site, tracing the foundations of the Twin Towers 70 feet underground.
3. Construction and FoundationBelow the Sept. 11 memorial plaza, with its two fountains outlining the footprints of the towers, the museum reaches down to bedrock, where the towers' steel columns were anchored. It's bounded by a slurry wall that kept back the Hudson River after the attack.
4. CostsThe plaza and museum together cost $700 million to build, subsidized with $390 million in tax-funded grants; officials hope the $24 museum entrance fee, expected to generate about $40 million a year, will help cover operating costs, expected to be about $60 million a year. Fundraising will cover the rest for now.
Jin Lee / National September 11 Memorial Museum / AP