A remarkable overhead view of the World Trade Center site, with the clearest visual outline yet of the north pool of the National September 11 Memorial and Museum, was released Tuesday by the Port Authority.

The photograph shows that the sunken pool, which marks the site of 1 World Trade Center, is now almost entirely framed out in structural steel, except for its southwest corner. Along the walls now defined by a network of columns and beams, waterfalls will descend from plaza level to the pool surface. At the center of the main pool — and also visible in this picture — will be a secondary depression, or void, into which the water will cascade out of sight.

Near the top of the picture, toward the left, one can see a wide swath of parallel diagonal lines. This marks the location of Fulton Street, under which a major east-west underground galleria will extend, linking the World Trade Center Transportation Hub with Battery Park City.

Near the bottom of the picture is a bright red trailer or shed, almost perfectly cubic. To the right are two concrete forms looking like small ziggurats. These were footings for the 460-ramp that served the site since the early days of recovery. The photo illustrates why it was so important to dismantle the ramp recently, in order to allow construction of the memorial to proceed.

At the lower right corner of the picture can be seen the “survivors’ stairway,” the last aboveground relic of the trade center, which stood on Vesey Street until last year. This structure will be incorporated into a staircase of the underground museum, although visitors will not be allowed to walk on it.

Along with the photograph, the authority announced that its project manager for the memorial, Thomas J. O’Connor, would be taking questions from the public through Friday.