NEW YORK (AP) — The Sept. 11 museum is taking shape 70 feet below ground, a cavernous space that provides an emotionally raw journey and ends at bedrock where huge surviving remnants and spacial voids reveal the scale of the devastation of what once was the World Trade Center.

The museum’s architects, director and two victims’ family members led members of the news media Tuesday on a tour of the subterranean space, which commemorates nearly 3,000 people who died in the 1993 and 2001 terrorist attacks.

There are no display cabinets yet, no exhibits. It is still a construction site. But it was easy to visualize the intent of the spaces, clearly articulated by the acute voids created by the fallen towers.

Authentic structural elements that survived the terrorist attacks are there: the slurry wall that kept the Hudson River from inundating the Financial District, the last column of trade center steel ceremonially removed from the site in 2002; the survivors’ staircase that served as an escape route for hundreds; and foundational box columns that anchored the building.

The slurry wall, still in place and measuring 60 feet by 60 feet, and the other huge artifacts define the museum’s design.

The $45 million museum occupies about 120,000 square feet beneath the 8-acre memorial plaza, the centerpiece of which is ‘‘Reflecting Absence,’’ two square reflecting pools set above the footprints of the north and south towers.

If the museum were above grade, said architect Steven Davis, a partner at Davis Brody Bond Aedas, ‘‘you’d be saying, ’Wow, how cool.’ But because it’s underground … the progress is less than evident.’’

Wearing hardhats and protective eye gear, the media reached bedrock level — where the main exhibition spaces will be located — along temporary wooden stairs and a freight elevator. The din of construction equipment was deafening at times.

When the museum opens in 2012, the tour will start at an above-ground glass pavilion, where a 665-foot long ‘‘ribbon,’’ or gently sloped ramp, will carry visitors through the site.

The ribbon — reminiscent of the ramp that workers used to build the original towers and during the recovery efforts following the attacks — will wind down 45 feet to the Memorial Hall, or lobby, past a three-pronged trident column recovered from the trade center rubble.

The memory of the twin towers is triggered from different areas of the museum by the depth of the memorial pools in the cavernous site. The pools will be clad in a recycled aluminum material similar to that used in the original towers. Special lighting will make them appear to be floating over the space.

‘‘They exist in true reference to their place and their position on the site so you can see immediately the relationship of the placement of the memorial pools with the actual location of the tower footprint itself,’’ Davis said. ‘‘This is something we thought was very important, this spatial accuracy.’’

Parapets of varying heights along the ramp will reveal different parts of the museum as visitors go down.

Museum architect Mark Wagner said the ramp is not intended to be a bold architectural statement, but rather an access path that allows the events of 9/11 to unfold. On Tuesday, it was still covered in rough concrete. The surface will be dark wood, while the underside will be muted, finished in dark, raw metal.

Stairs or an escalator will provide the final 25-foot descent to bedrock, and to a trapezoidal expanse containing the 60-foot high slurry wall that held back the Hudson.

‘‘You begin to understand that the slurry wall is the separation between the basement of the original trade center’’ and the river, Davis said.

The last standing 36-foot steel column that was removed from the trade center debris at the end of the nine-month recovery effort in 2002 stands in front of the slurry wall. It became a spontaneous memorial to the victims; construction workers and family members covered it with tributes, photographs and inscriptions. On Tuesday, it was sheathed in a climate-controlled covering.

The tower’s foundational steel box columns are exposed at bedrock in the floor slabs, providing an outline of the buildings. The federal government said the column bases and slurry wall should remain in place.

The final descent runs parallel to the Vesey Street stairs, known as the survivors’ staircase, encased in wooden scaffolding on Tuesday. The 37 steps served as an escape route for people fleeing. It stood for years as the last remaining above-ground remnant of the original complex.

There are also several places where visitors can stand between the remnants of the two towers.

Thousands of unidentified remains of 9/11 victims will be stored in the museum, in an area reserved for the medical examiner’s office; an adjacent room will be set aside for family members. These areas will be off limits to the public.

A quotation from Virgil’s ‘‘Aeneid’’, ‘‘No Day Shall Erase You From the Memory of Time,’’ will be incised into the wall that separates the private and public spaces.

‘‘The wall is only a membrane that separates us from them, and it’s our obligation to remember,’’ said museum director Alice Greenwald.

Anthoula Katsimatides, whose brother died in the attacks, said she hoped visitors will ‘‘learn something about one of those beautiful people who passed away on that day’’ and come away with ‘‘a sense of peace and a sense of hope.’’

The idea for the museum design began with ‘‘all the things we were given,’’ the remnants of the complex.

‘‘A traditional museum design is an icon which contains exhibits,’’ he said. ‘‘But this museum, the icon is the exhibit.’’