ARLINGTON, Va. — For tourists, the new memorial to 184 people who died at the Pentagon in the September 11, 2001, terrorist attacks is not especially convenient. Nor is it ideal from a security perspective to have 24-hour public access right outside the American military’s nerve center.

But there is little dispute that the new memorial, which opens to the public Thursday, was built right where it should have been: at the spot where American Airlines Flight 77 plowed into the west wall of the Pentagon.

“This is hallowed ground,” James Laychak, whose brother, David Laychak, was killed in the attack, said.

Defense Secretary Robert Gates will speak at a ceremony dedicating the memorial Thursday morning. It opens to the public that evening.

The memorial, built on an angle parallel to the plane’s path just before it crashed, consists primarily of 184 cantilevered benches, each bearing a victim’s name.

The two-acre park will be open 24 hours a day, seven days a week, and will be patrolled by the Pentagon Police Department. While it is just a short walk from a Metro subway station, it is on a patch of land previously trafficked almost exclusively by Pentagon workers.

Deputy chief of operations for the Pentagon Police Department, William Stout, acknowledged some ambivalence about the location.

“If you’re asking me as deputy chief of operations if I’m happy with the location, I’d have to say ‘no,'” Mr. Stout said. “But overall, it seems logical to me to have it here. … We’ll have eyes on it all the time.”

It was not a given that the memorial would be located at the site of the crash. The Pentagon suggested about 10 different options. But family members were adamant that the memorial be built where the plane hit, Mr. Laychak said.

Mr. Laychak, also president of the Pentagon Memorial Fund, said the fund has already raised the $22 million needed to build the memorial, but fundraising efforts continue to help pay for its upkeep.

Mr. Laychak said he is curious to see how the public will react to and interact with the Pentagon Memorial. He believes its design puts visitors in a reflective state of mind.

“I look forward to seeing some of the customs and traditions that will develop,” he said, referring to traditions that started spontaneously at other memorials, like the pencil rubbings of names on the Vietnam memorial.

The Pentagon Memorial emphasizes the diversity of those who died there. The benches are arranged by the victims’ ages, so the first one visitors see as they enter is dedicated to a 3-year-old passenger on Flight 77, Dana Falkenberg, and the last to a retired Navy captain, John Yamnicky, another passenger who was 71.

Paper bark maple trees have been planted throughout the memorial, selected because they retain their leaves late into fall and turn a deep red when the colors change, a spokeswoman for the Pentagon Renovation Program, Lea Hutchins, said.

From the memorial, the rebuilt section of the Pentagon remains clearly visible, the new limestone a slightly lighter shade than the old. Planes coming in to nearby Reagan National Airport fly low and loud along the Potomac River.

Mr. Laychak, for all the time he has spent at the memorial, has not yet visited the bench engraved with his brother’s name. He is waiting for memorial’s dedication so he can see it for the first time together with his family.

“I wanted to save that moment,” he said.