When you’re dealing with elephants, you need to up the size and scope of a project.

The 35-ft-tall walls of the new 6.25-acre Elephant Lands habitat at Portland’s Oregon Zoo mark a key project milestone for the elephant facility. Crews from Lease Crutcher Lewis started setting the walls this month, part of an effort to finish off the $53 million project in 2015.

The new exhibit, a portion of an effort to complete eight major projects at the state’s largest zoo, will feature two indoor spaces four times larger than the current habitat.

With its solid 35-foot-tall walls, this section of the indoor habitat is now the largest building in the zoo's 125-year history, but it won't hold that record for long. The even larger Forest Hall portion of the habitat will exceed that mark.

"We've turned a major corner," says zoo bond project engineer Wayne Starkey in a statement. "A lot of construction is behind the scenes, and people don't often get to see the progress we're making until a habitat is complete. With the walls up, you can now understand the scale of this project. This is the most ambitious stage of the most ambitious project in the zoo's history."

The 14,000-square-foot holding area—with three 1,600-square-foot stalls for elephant care—will replace the zoo's current holding area, which dates to 1959. Together with Forest Hall, the two indoor spaces will sit on 32,000 square feet, with a roof reaching up to 43 feet at its highest point.

As the indoor space takes shape, the project represents the largest building on the zoo grounds in Portland’s Washington Park. Elephants can match giraffes and reach up to 24 ft. Oregon Zoo elephants have been known to stand on their hind legs and punch holes in shorter ceilings with their trunk, an obviously enjoyable endeavor for an elephant looking for fun.

The new habitat will extend around the eastern edge of the zoo, from the south of the current elephant habitat north into the area that formerly housed Elk Meadow. A few features include foundations covered with four ft of sand to act as a cushion for elephants’ feet and a roof with solar panels and 8,600 sq ft of green roof to decrease runoff.

An elephant-sized "air curtain" separating Forest Hall from the outdoor areas will maintain a constant, comfortable indoor temperature for pachyderms and visitors while providing the herd around-the-clock access to the rest of Elephant Lands' 6.25-acre spread.

"We've designed a world-class home that honors this amazing species," Kim Smith, zoo director, says in a statement. "Elephant Lands is all about elephants having choices and activity. We think it's going to be a game-changer for elephants worldwide and help raise the bar for animal welfare."

The habitat will also feature new views of the zoo’s herd with visitors enjoying elevated walkways with views into the habitat. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.