Phase two of Amazon’s $2.5-billion HQ2 development in Northern Virginia will have an outdoor vibe reminiscent of the e-retailing giant’s Pacific Northwest roots, according to designs released Feb. 2.

With construction already underway on two new office towers at the National Landing complex located across the Potomac River from Washington, D.C., the proposed next phase, called PenPlace, will be centered around “The Helix,” a 350-ft tall tapered glass structure accented with two exterior landscaped nature trails that spiral their way to the top. Amazon officials characterize the structure as an “alternative workspace” for employee collaboration and down time.

The Helix and the rest of Phase 2 is being designed by NBBJ of Seattle. The firm opened a DC office last July to support HQ2, among other things.

In addition, PenPlace will include three 22-story office buildings totaling 2.8 million sq ft to accommodate 13,000 employees. Major elements of the planned 2.5 acres of outdoor space include a 250-seat amphitheater, a variety of landscaped areas and plazas and a European-style retail village with wood-framed pavilions showcasing locally owned shops and restaurants.

While PenPlace will feature multiple pedestrian walkways and surface spaces for more than 950 bicycles, cars and service/delivery vehicles will be routed to underground parking and docking areas. Targeting LEED Platinum ratings, the office buildings will include rainwater recycling systems and feature daylighting and natural ventilation.

The complex’s pedestrian-oriented, high-sustainability profile is a radical departure from the canyons of high-rise office and condominium buildings that distinguish older areas of National Landing, originally named Crystal City and Pentagon City due to the latter’s proximity to the U.S. Dept. of Defense headquarters.

One of Crystal City’s defining features was its network of tunnels linking buildings with underground retail areas and one of the area’s three Metrorail stations, virtually eliminating the need for workers and residents to venture outdoors.

Pending approval by local officials, PenPlace could break ground as early as next year with construction to be complete in 2025. At full build-out, Amazon’s HQ2 will house 25,000 employees.

National Landing is bustling with other construction projects, including long-planned transportation infrastructure upgrades that were fast-tracked by the state and Arlington County during the intense multi-city competition for HQ2. Infused with $270 million in state and federal funding, the projects include upgrades to an adjacent freight and passenger rail corridor, new protected bike lanes and a pedestrian bridge across the George Washington Memorial Parkway to Reagan National Airport.

An elevated highway is also set to be transformed into a multi-modal urban boulevard, while the area’s southernmost Metrorail station is being augmented with new entrances.

JBG Smith, Amazon’s development partner and owner of several developed and undeveloped parcels in National Landing, recently acquired a 1970s-era motel in the area with plans to turn the site into a 500,000-sq-ft multi-family development.