INSIDE THE HELIX: AMAZON'S DOUBLE-SPIRAL TOWER AT HQ2 — AND WHY IT STILL HASN'T BEEN BUILT

By Virginia Viadas

The Helix was designed to be the East Coast answer to Amazon's Seattle Spheres: a 350-foot double-spiral tower wrapped in two walkable landscaped paths, filled with plants drawn from Virginia's Blue Ridge Mountains, and open to the public on select weekends. Four years after Arlington County unanimously approved it, the site remains an empty 11-acre block. As of mid-2026, vertical construction has never begun.

Project fact sheet

What the building was supposed to be

The Helix borrows its logic from the Spheres but inverts the geometry. Where the Seattle structure encloses a conservatory behind glass, the Arlington building takes the double helix as its organizing form — a shape Amazon connected to DNA, galaxies, weather patterns, pinecones and seashells — and offers alternative work environments among gardens and trees native to the region.

The defining move is on the outside. Two walkable paths of landscaped terrain spiral up the building's exterior, planted with species familiar to hikers of Virginia's Blue Ridge Mountains. Inside, the program calls for formal and casual meeting spaces set among more than 25,000 square feet of planting areas and living walls. The building was also to house an artist-in-residence program, a 1,500-person meeting center, and an outdoor hill climb open to the public on select weekends each month.

The engineering problem nobody talks about

Put plainly: a spiral of soil wrapped around a 350-foot steel-and-glass tower is a structural and mechanical problem before it is an architectural one. Four constraints define it:

1. Saturated soil weight. Planting medium at irrigation capacity is dramatically heavier than dry soil. Every terrace has to be designed for the wet condition, not the delivered condition, and that governs the frame.

2. Wind at elevation. Mature trees at 300 feet experience wind loading that ground-level landscaping never sees. Root balls need mechanical anchoring, and the trees themselves become a dynamic load on the structure.

3. Waterproofing over occupied space. A continuous planted ramp is a continuous roof assembly over interior floors. Root barriers, drainage layers and redundant membranes are not optional, and any failure is invisible until it appears three levels below.

4. Irrigation and drainage as a vertical system. Water has to be lifted, distributed and then collected without overwhelming the storm system during a heavy rain event, which typically means detention capacity built into the terraces themselves.

These are solved problems — Milan's Bosco Verticale and Singapore's CapitaSpring demonstrate as much — but they are solved expensively. The cost premium is concentrated in structure, waterproofing and long-term horticultural maintenance, none of which produce leasable area.

The larger campus

PenPlace was planned as 3.3 million square feet of additional commercial space across three more 22-story office towers capable of housing up to 13,000 additional employees, anchored by the Helix as an indoor garden and corporate conference center. The three towers target LEED Platinum certification. The site also included 2.5 acres of public open space with an amphitheater, dog run, retail pavilions and restaurants, with all vehicle access moved underground to prioritize pedestrian circulation.

On energy, Amazon committed to powering HQ2 operations entirely with renewable energy, contracting 82 megawatts from a new 120-megawatt solar farm in Pittsylvania County, Virginia, expected to generate 172,500 megawatt-hours annually, in line with its net-zero-by-2040 Climate Pledge. A revised design also doubled the number of rooftop solar panels and integrated them into the buildings' skyline profiles.

Timeline of the pause

Where it stands in 2026

Phase 1, Metropolitan Park, is fully operational with roughly 8,500 employees. Phase 2 remains on hold with no confirmed construction start date as of mid-2026, and the June 2025 extension was widely read as a formal acknowledgment that the phase was not happening on any near-term schedule.

Reporting in April 2026 noted that HQ2 employment had barely moved over the prior year, against a backdrop of roughly 30,000 companywide job cuts that local planners say now factor into Amazon's space-planning decisions. By June 2026, the company was reportedly weighing temporary uses for the fenced 11-acre block, including open green space, temporary art installations and a pop-up dog park.

An Amazon representative has said the company has ample space at Metropolitan Park but still views PenPlace as a long-term investment.

What a restart would require

Three conditions, in order of difficulty:

1. Demand. Three 22-story towers only pencil out against sustained headcount growth. Flat employment is the binding constraint, not construction cost.
2. Schedule against the 2028 deadline. Construction must commence before June 30, 2028, or Amazon needs another extension or a revised site plan.
3. Repricing the design. Construction costs have shifted materially since the 2022 approval. A signature building with a landscaped exterior ramp is precisely the kind of element that gets value-engineered when a project is rebudgeted years later.

That last point is the one worth watching. Buildings like the Helix survive pauses only when the client treats them as brand infrastructure rather than as real estate. The Spheres cleared that bar in Seattle. Whether the Helix clears it in Arlington is now a question of when — or whether — Amazon needs the space.

Frequently asked questions

What is the Amazon Helix? A planned 350-foot, double-helix-shaped building at Amazon's HQ2 Phase 2 in Arlington, Virginia, designed by NBBJ with two landscaped walkable paths spiraling up its exterior and more than 25,000 square feet of interior planting.

Has the Helix been built? No. Amazon announced an indefinite pause in March 2023. Underground utility work was completed, but vertical construction has never begun.

When will construction start? There is no confirmed start date. Arlington County extended the site plan's validity to June 30, 2028, giving Amazon until then to commence construction.

How is the Helix different from the Amazon Spheres? The Spheres in Seattle are glass conservatories enclosing a plant collection. The Helix places its landscape on the outside, as two spiraling walkable terraces, and functions primarily as a meeting and amenity building.

Who designed the Helix? NBBJ is the architect, SCAPE the landscape architect, and Whiting-Turner was named contractor for PenPlace.

Was the project approved? Yes. The Arlington County Board approved the PenPlace site plan unanimously in April 2022.

Sources: Amazon, NBBJ, Arlington County, Building Design+Construction, CoStar, Washington Business Journal via Hoodline, ARLnow, Northern Virginia Magazine, Axios, WJLA.