Sunday is a famous Dallasite's birthday: Reunion Tower.

The downtown landmark, and the most recognizable building in the skyline, opened to the public 40 years ago on April 15, 1978.

Here are a few things you might not know about the tower:

The initial design didn’t feature a ball on top. A miniature design, shown in a photograph in the Dallas Morning News on Oct. 16, 1973, showed a glass-like tower with a pyramid-like design on top, not the soon-to-be iconic ball.

Another mockup, shown in a brochure for the project, showed a tower with a cap-like observation deck on top.

Courtesy of Reunion Tower.
Courtesy of Reunion Tower.
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Reunion was named after the “La Reunion” Utopian community, where French, Belgian, and Swiss immigrants had settled in the 1850s.

The Reunion Ball weighs 500 tons and is 19,549 square feet. About 2 miles of aluminum pipe forms the globe-like structure, the Morning News reported in December 1977, when the project was finished.

Dallas Morning News clippings from 1977, courtesy of Reunion Tower.
Dallas Morning News clippings from 1977, courtesy of Reunion Tower.

The land was pretty cheap. Ray L. Hunt bought the first 20 acres for the project for $2.92 per square foot. The location was a mostly vacant corner of downtown, behind the then-closed (at the time) Union Station.

The 560-foot tower is the 15th tallest building in Dallas. If you’re taking the stairs, that’ll be 837 steps to the top. At the top, there's a restaurant, Five Sixty, along with a separate floor with an observation deck and cafe.

Most people take the elevator, though, which takes 68 seconds to the top. A couple got married during the one-plus minute ride to the top shortly after the tower opened.

Proposals are popular, yes, but not many like this one. Within a year of the tower's opening, a man proposed to his girlfriend at the restaurant – by hiring a single-engine plane to fly around the tower with a banner that read, “Patty, will you marry me?”

It's basically a movie star. The gleaming Hyatt Hotel and the base of the tower is known for appearing in the opening credits of the TV show “Dallas.” But the tower has also appeared in Robocop (along with the rest of downtown Dallas), “The Lathe of Heaven,” “The Tree of Life” and “Asteroid.”