One of downtown Dallas' most recognizable skyscrapers is up for sale.

It's hard to miss the 37-story Whitacre Tower with its huge blue AT&T emblems and new nightly light shows.

Since 2008, the Akard Street high-rise has been owned by a unit of billionaire New York investor Carl Icahn's property firm. The almost 1-million-square-foot tower is the largest building in AT&T's four-building downtown headquarters campus.

Icahn Enterprises has hired commercial property firm CBRE to market the office high-rise to potential buyers. The office building has been listed on CBRE's international property sales website.

AT&T's global headquarters lease in the property runs through 2030. The sale is expected to bring in at least $250 million.

The telecom giant recently announced plans to spend more than $100 million to upgrade the four-block area it occupies on the south side of downtown. AT&T owns the other three large buildings on the property.

Icahn bought the Dallas tower 10 years ago along with other AT&T properties in Atlanta and other markets.

"AT&T owns all of the buildings in our downtown Dallas campus, except Whitacre Tower, which is owned by Icahn Enterprises," an AT&T spokesman said. "If building ownership changes, it won't impact our lease agreement."

Built in 1982, the Whitacre Tower in downtown Dallas was originally occupied by regional offices for Southwestern Bell.

In 2008, AT&T moved its headquarters from San Antonio to the downtown Dallas campus where it now has more than 6,000 workers.

After looking at several options — including a move to the suburbs — AT&T in 2016 decided to keep its global base downtown and make significant improvements to the campus.

Construction is now underway along Commerce and Akard streets to enhance public and pedestrian areas and add amenities for workers in the complex.