The 9/11 Museum, located where the Twin Towers once stood, explores the history of the 9/11 terrorist attacks. The museum houses artifacts, historical records, firefighting equipment and a memorial exhibition. Tours with expert guides are available.
Outside the museum is the memorial, which honors the 2,977 people killed in the terror attacks of September 11, 2001 at the World Trade Center site, near Shanksville, Pennsylvania, and at the Pentagon, as well as the six people killed in the World Trade Center bombing on February 26, 1993. The Memorial’s twin reflecting pools are each nearly an acre in size and feature the largest man-made waterfalls in North America. Outdoor memorial audio guides are available for purchase on site. While outside, also look for the 9/11 Memorial Glade and The Survivor Tree.
Here's the full guide to visiting the 9/11 Museum & Memorial.