The Charles and Dee Wyly Theatre was “topped out” this morning — the traditional ceremony marks the highest point of construction on a building; in this case, nine stories straight up. With an applauding crowd of donors and dignitaries present, including Mayor Tom Leppert, Dallas Center for the Performing Arts president Bill Lively and chief donor Charles Wyly, an apple-green I-beam covered with autographs was hoisted overhead and put in place.

DCPA chair Howard Hallam took the occasion to note that construction of the Wyly was on time and under budget. Opening night, he declared, would be precisely 17 months and eight days from today. (The apple green color was chosen to match what will be the color of the theater’s seats — though they won’t be quite as bright, board member Deedie Rose assured the crowd.)

It’s fitting that the height of the Wyly should be commemorated. The 600-seat performance space — the future home of the Dallas Theater Center — represents a radical, “vertical” departure from conventional theater design. It will be unlike any theater, anywhere, because the “backstage” support facilities (costume and scene shops, rehearsal rooms) as well as the “front of house” amenities (lobby, restrooms, concessions) will not be clustered around or behind the auditorium. They will be stacked on top of it or underneath it (In addition to nine floors aboveground, the Wyly has three floors underground.).

The Wyly, in effect, will be the world’s first skyscraper theater. But the Wyly is doubly daring– at least.

Chief designer Joshua Prince-Ramus — of the New York office of Rem Koolhaas’ firm, OMA — has given the building an innovative support structure, permitting its “open-skin” appearance, one that the DCPA and Theater Center have touted: All of the steel girders that currently hold up the structure (in the photos, the big ones on the corners, for instance) will be removed by summer’s end. The entire structure will be supported by the concrete wall along one side and the criss-crossing poured-cement beams along the others. This will allow the first three floors to be sheathed entirely by tall glass windows (along three sides of the box), making the auditorium “see-through.” Built-in curtains will shut out the sunlight or prying eyes when necessary, while the seating will be held up by three support lifts that can raise, lower or reconfigure the audience. Visually, the theater will look as strikingly different as it actually is in its thinking and internal structure: The top six floors of the Wyly, coated with extruded aluminum tubes, will appear to float on top of this glass bubble on the ground.