BOSTON -- A glass cube sits at the highest spot on two beautifully landscaped acres of land at Logan Airport in Boston. Inside, twin towers mark the time that American Airlines Flight 11, and United Airlines Flight 175, took off from Logan on Sept. 11, 2001. On each plate, etched on glass, are the 148 names of all who died aboard both flights.

"It still stabs me in the heart to know she's a part of it, she's there," said Joan Greener, who lost her niece, Karen Martin, the head flight attendant on Flight 11.

The memorial will be formally unveiled on Tuesday. But Greener and her daughter, Michelle Pare, saw the memorial on Saturday, reported WCVB-TV in Boston. They said they were especially moved by the memorial's ceiling, made up of squares of glass reflecting the light in different ways. The designers meant it to convey the idea of a fractured sky and more.

"It kind of reminded me of the human spirit. How, you know, all these people were like lights in our lives," Pare said.

For the family of Judith Larocque, a passenger on Flight 11, the memorial is too painful. Reached by telephone in New York, her daughter said she will stay away.

"While others may find it a comforting place, remembering my mom's last moments is not something that we find comfort in. We prefer to remember the rest of her life, not the end of it," Carie Lemack said.

"We're all trying to move on. But on the other hand, they shouldn't be forgotten, and this day shouldn't be forgotten," Greener said.

Logan Airport officials have said they understand the mixed feelings about the memorial. But Sept. 11 was an event of such enormity, they felt it necessary and proper to leave something behind for future generations.