Fifteen years ago this month, terrorist attacks on New York City and Washington D.C. killed thousands and shocked the world. On Sept. 11 in both cities there will be numerous events to pay tribute to the fallen, but some will be open only to families of victims.

New York City

Memorial Ceremony at World Trade Center Site

This memorial ceremony, open only to families of 9/11 victims, will be televised (check local listings). The ceremony begins at 8:30 a.m. and is expected to conclude at noon.

9/11 Memorial Museum

This museum, which sits between two reflecting pools of the 9/11 Memorial, will be closed to public and only open to families of the victims on Sept. 11. 9/11 Memorial Museum. 180 Greenwich Street, New York. 911memorial.org/museum

Service at St. Paul's Chapel

St. Paul's Chapel sits directly across from where the World Trade Center towers previously stood. It remains a place of rest and refuge. On Sept. 11, numerous activities to honor the memories of 9/11 victims and will take place beginning a 8 a.m. Services will take place in St. Paul's Churchyard while the chapel is undergoing restoration work. trinitywallstreet.org

9/11 Reflections concert

Art breathes life and a combination of singing, poetry readings, orchestra and art exhibit will be held in homage to those lost on 9/11. The concert will take place at St. Malachy's Church from 4 to 5 p.m. Tickets are $25 in advance and $35 at the door. St. Malachy's Church. 239 West 49th Street, New York. salvatones.org

Washington, D.C.

Pentagon Memorial

One hundred eighty four people were killed when American Airlines Flight 77 crashed into the Pentagon on 9/11. On Sept. 11, the memorial will be closed from 7 a.m. to 11 a.m. for a private event for family of victims and will resume normal hours afterward. This memorial is free for visitors and open 24 hours a day every day of the year. Pentagon Memorial. 1 North Rotary Road, Arlington, Virginia. pentagonmemorial.org

A moment of silence will be observed at 9:37 a.m. on 9/11, to mark the moment when American Airlines Flight 77 crashed. The cemetery will be open to the general public for visits all day. arlingtoncemetery.mil

Unity Walk

An annual event, the Unity Walk was created to encourage fellowship, solidarity and friendship among people from all faiths and cultures. The walk convenes on Massachusetts Avenue and stops at religious houses and centers throughout the D.C. area. ifcmw.org

National Day of Service

Congress marked Sept. 11 as a National Day of Service and Remembrance in 2009. Those interested in commemorating the tragedy with action can sign up to volunteer on Sept. 10 and 11. serve.gov