Dallas-based telecom giant AT&T plans to spend $100 million revamping its downtown Dallas headquarters.

AT&T also will add 500 workers to its 5,800 employees in its buildings on the south side of downtown.

The planned renovations would be one of the largest such office building redos on the way for downtown Dallas.

"This is in addition to the $100 million we have already invested in this campus," said Michael Peterson, AT&T regional vice president. "We have more than doubled our employees since we moved here in 2008.

"We are hoping to recharge a lot of this campus and turn it into a real destination."

AT&T unveiled preliminary downtown design plans this week for the first time. The biggest changes are on the way at street level, where AT&T intends to expand landscaped plaza areas, and add eateries and shops.

"Our vision is to help transform this campus into a destination place for tourists and downtown residents as well as our employees," Peterson said. "We are calling this the AT&T Discovery District."

The company also wants to close almost three blocks of Akard and Jackson streets to vehicles as part of the new pedestrian plan.

AT&T's downtown campus takes up four blocks and has six office and parking buildings. (AT&T)

In October, AT&T said it had decided to keep its international headquarters in its existing downtown buildings after looking at several alternatives.

AT&T has more than 2 million square feet of operations along Akard Street in four buildings built between 1929 and 1984.

Peterson said the company will meet this week with the city's transportation committee to talk about the proposed street closures.

AT&T also will present its proposals next month to the Dallas City Plan Commission and the city's economic development committee to talk about potential incentives for some of the public improvements.

"We have been in discussions with the city and DART and Downtown Dallas Inc. and our neighbors all around us to make sure this vision works for all of us," Peterson said. "It will necessitate some changes in the streets in order to enhance the traffic flow and make this district more pedestrian friendly."

Kourtny Garrett, president of the economic development group Downtown Dallas, said there is support for AT&T's plans.

"The degree of investment and what they are doing in this neighborhood will serve as a catalyst in the southern area of downtown," Garrett said. "It's the vision they are bringing with that investment and turning the campus inside out.

"It's bringing what you think of when you think of the global AT&T headquarters," she said. "You will now be able to see it on the exterior."

With more than $146 billion in annual revenue, AT&T is the largest company based in Dallas and the second-largest in all of North Texas — behind only Irving's Exxon Mobil Corp.

The company has over 240,000 workers worldwide and is the largest private-sector employer in downtown Dallas.

One of the more visible changes at its downtown office would be along Commerce Street, where a large glass canopy would be constructed extending over the sidewalk and a traffic lane.

"We are looking to expand our sidewalk along Commerce Street and put in a drop-off for our customers and our visitors," Peterson said. "We average about 250 visitors a day, and right now we really don't have a front door."

The existing plaza on the south side of Commerce will be totally rebuilt.

"There will be new planting and new water features," Peterson said. "There is a raised green space with restaurants and retail all around it. There is outdoor art and fountains.

"We want to make this place inviting to visitors and downtown."

AT&T has already begun making minor changes on the east side of its 37-story Whitacre Tower on Browder Street.

The company still has about six months of planning work to do and must receive city approvals before the biggest work begins.

"We plan to have the whole project completed sometime in 2019," Peterson said.