As part of a dedication period offering tribute to the nearly 3,000 souls who died on September 11, 2001, the 9/11 Memorial Museum opened its doors in 2011 to survivors, first-hand witnesses, and responders.

Here are 9 facts of the museum worth knowing:  

1) Encompassing 110,000 square feet of space, the 9/11 Memorial Museum — which honors the victims of terrorist attacks on both September 11, 2001, and February 26, 1993 — cost $700 million to build. The funds were through private and public donations.

2) Both the 9/11 Memorial and Museum occupy about eight acres of the original World Trade Center site.

3) Big numbers: Expect to see 23,000 images, 10,300 artifacts, 500 hours of moving images and 1,970 oral histories.

4) Tissues and exit doors are strategically placed for visitors who may become overwrought with emotion. 

"Ultimately, this Museum will express what those who attacked us did not understand—that the ties that bind us strengthen in the most extraordinary ways when we are faced with the most unimaginable circumstances." -9/11 Memorial President Joe Daniels.

5) To get into the museum, visitors must walk through a steel and glass pavilion that include two massive steel tridents, which had been part of the Twin Towers.  

6) To get to the main exhibition space, visitors descend to bedrock alongside the Vesey Street Stair remnant known as the "Survivors’ Stairs," where hundreds escaped death on 9/11. 

7) The museum is separated into three core sections: the historical, memorial, and foundation hall exhibitions. The historical delineates the events that led up to September 11th; the memorial puts a human face to the thousands of people who died in the September 11, 2001, and February 26, 1993, terrorist attacks; the foundation hall offers reflection, hope, and the spirit of determination through its slurry wall, a massive retaining wall from the original World Trade Center that withstood the 9/11 destruction.

8) The museum includes an Education Center to inform student and teacher groups, as well as to hold seminars. 

9) For more information, go to the museum's official website:

All images in the photo gallery are credited to Jin Lee.