Chicago-based developer Amli Residential is building the tallest tower in Dallas in three decades.

The 45-story apartment high-rise will go up on Field Street on downtown's north side.

When the folks at Amli started planning the high-profile tower, they knew it had to be more than just another glass and concrete box.

The development site is next door to one of Dallas' most recognizable skyscrapers — the rocket-shaped Fountain Place.

"It was of the utmost importance we do something unique and different being next to I.M. Pei's Fountain Place," said Amli executive vice president Taylor Bowen. "We want to have one of the premier timeless buildings downtown."

That's a tall order in Dallas, where the skyline has its share of standout buildings.

Amli hired Austin-based architect Page Southerland Page Inc. to design its $150 million residential high-rise. It will be the tallest new downtown building since the 55-story Chase Tower opened in 1987.

The building will sit on a site that was originally earmarked for a second-phase tower at Fountain Place. The matching skyscrapers were to have been joined by the ground-level water gardens.

"This was master-planned a long time ago to have two towers on either side of the garden," said Page senior principal Lawrence Speck. "We couldn't do a twin — it's a residential tower instead of an office tower. We wanted the buildings to seem like siblings, not twins."

Page's design looks like a pointed prism of green glass.

"We wanted a very clean, geometric object and the two towers will dance with each other across the garden," Speck said. "It really will be distinctive on the skyline — the kind of signature just another box would never be."

Fountain Place is a tough act to follow.

When designs for the Dallas skyscraper were unveiled in the fall of 1983, it was hailed as one of the country's most dramatic new towers.

Designed by architects Harry Weese and Harry Cobb with I.M. Pei and Associates, Fountain Place won accolades for its sculptural shape and the lush cypress gardens at the base.

"Everybody is very conscious of the historical significance of that garden," which was designed by late landscape architect Dan Kiley, said Speck. "It will also make the garden more interesting and lively because now there will be people there 24/7."

The 367-unit apartment tower will take about two years to build.

Rental units in the Amli Fountain Place high-rise will be larger than usual — about 1,250 square feet. Rents for the units have not been set, but such high-rise apartments typically fetch as much as $3 per square foot.

A pool deck with outdoor lounge areas will be constructed on top of the parking garage built into the base of the new tower. The entire skyscraper will be sheathed in virtually the same glass as Fountain Place.

"The glass needed to be the primary connection between the two buildings," Speck said. "We looked at tons and tons of alternatives and did testing.

"Making glass for a tower in 2017 is a complete different enterprise than making glass in the 1980s," he said. "The glass now has to perform much better."

Construction of Amli's apartment tower is just one of the changes coming at Fountain Place.

Owner Goddard Investment Group, which bought the tower in 2014, is constructing an adjoining parking garage and retail building. And renovations will open up the ground-floor lobby of the office tower.

Architects Gensler and James Carpenter Design Associates did the work on the Fountain Place renovation and construction of the garage and retail addition.

Amli purchased the vacant site — for decades used as a parking lot — in March.

"The new Amli tower is significant because it will create a true mixed-use environment at the highest level," said Johnny Johnson with Cushman & Wakefield, which markets the Fountain Place offices to tenants. "The energy sparked by the pedestrian experience will enhance the complex and everything that surrounds it.

"It will make Fountain Place an even more desirable place to be."

Amli is one of the country's largest and most experienced apartment builders, investors and operators.

The company owns the 24-story 1400 Hi-Line apartment tower in Dallas' Design District, along with about a dozen more apartment communities in North Texas.

Bowen said the Fountain Place apartment tower will be one of his firm's largest and most significant developments. "We felt with the location, it must be a great building," he said.

The project will be one of about a dozen high-rise residential buildings under construction in the Dallas area.

Four high-rise apartment buildings are opening this year in the nearby Victory Park development just northwest of downtown.

There already are some signs of softening in that sector, said Dallas apartment analyst Mike Puls with Foley & Puls.

"Rents have stopped going up in one-bedroom units in high-rises," Puls said. "A few unit types are actually going down in the poor properties."

But since Amli's project will take about 24 months to build, all of the current high-rise rental developments will already have hit the market by then and should be substantially leased.