One of downtown Dallas' most familiar towers is in the midst of a major makeover that will bring additional parking and a new look to the Big D skyline.

Owners of the 60-story rocket-shaped Fountain Place are spending more than $70 million on the office building.

At the same time, another developer is breaking ground on a 45-story companion tower next door.

Atlanta-based Goddard Investment Group — which bought Fountain Place in 2014 — is building a new garage and retail building on the northeast side of the green glass tower.

The upgrades to the 31-year-old Ross Avenue skyscraper have already prompted several major tenants to sign up for longer leases in the building.

Wells Fargo Bank — which had been looking at other options in downtown and Uptown — has committed to keeping 123,650 square feet in Fountain Place for its flagship Dallas location.

Bracewell LLP, Tenet Healthcare, Hunton & Williams and investment firm Gerald L. Ray & Associates have also decided to stay in the tower.

In all, more than 500,000 square feet of extended office deals have been signed in the 1.2 million square foot building, according to property agents at Cushman & Wakefield of Texas who lease the tower.

"The renewals and new leases are an absolute validation of the vision of Goddard Investment Group and their commitment to such a significant reinvestment in an iconic Dallas property," Cushman & Wakefield's Johnny Johnson said.

Revamping Fountain Place wasn't something the new owners rushed into.

Designed by Harry Cobb of I.M. Pei and Partners, the building is one of Dallas' most iconic skyscrapers and a standout on the city's skyline.

Goddard hired New York-based James Carpenter Design Associates Inc. and Gensler to lead the team working on Fountain Place.

The current construction includes:

· Building a 10-story, 1,500-space parking garage with ground-floor retail between Fountain Place and the next-door Fairmont Hotel.

· Renovation of the tower's lobby, including a floor-to-ceiling, glass-wall art piece designed by James Carpenter.

· A new tenant lounge constructed at the north end of the lobby.

· An 8,000-square-foot fitness center.

· A training room to accommodate up to 150 people.

The upgrades will also include renovation of the tower's signature fountains and landscaping around the base.

The renovations will include new art glass walls in the lobby. (Goddard Investment)

Most of the work will be done by early next year.

"Our business is acquiring properties where we see potential for dramatic improvement," Jim Wilson, Goddard principal, said in a statement. "We saw the impact of Klyde Warren Park and the growth of the southern segment of Uptown extending into the Arts District and Ross Avenue.

"At the same time, we saw parking lots surrounding Fountain Place being acquired by some of the most successful investors in Dallas, who had exciting plans for the properties," he said. "So, we saw that area as being on the cusp of an upswing."

Fountain Place is just the latest of several Ross Avenue towers to undergo redevelopment. Owners of the 1980s buildings are hoping to head off more tenants moving to new buildings in Uptown.

Owners of the nearby Trammell Crow Center recently started a $135 million renovation that includes construction of a new parking, retail and hotel building across the street.

Fountain Place is currently 85 percent leased. But almost 300,000 square feet of the tower will come vacant in 2017 when the Environmental Protection Agency moves out of its longtime offices.

"Given the market and what's going on downtown, we are very pleased," said Johnson, who worked on the leases with Cushman & Wakefield's Lauren Napper. "With the redevelopment, we are able to position the building in a different light."

Goddard just sold the vacant lot on the north side of Fountain Place to Chicago-based builder Amli Residential.

Amli has begun site work for a 45-story, 367-unit apartment tower at the corner of Field Street and Munger Avenue.

The new tower will also be covered in green glass and has an angular shape.

The apartment high-rise will open in 2019.

"People today are looking for a 24/7 environment, and that's what we're creating at Fountain Place, a real destination" Wilson said. "Our intention is to create the finest office building in this part of the country, but we're able to charge lease rates that are significantly lower than rents in Uptown."