More than half a decade after launching the largest economic development sweepstakes in recent history, Amazon has completed construction on the first phase of its second headquarters in Arlington, Virginia.

On Monday, hundreds of employees began working in the pair of 22-story office towers that make up the first phase of HQ2, marking a major milestone in the massive development, Amazon announced in a release.

The buildings, totaling 2.1M SF of office space, are eventually slated to host 12,500 Amazon employees. The company is shifting employees into the buildings in phases from nearby offices it temporarily leased during construction, and it expects to have 8,000 people working there by this fall, a spokesperson said.

The company as of May 1 has required employees to work in offices at least three days a week, and thousands of workers returned to the company's Seattle headquarters earlier this month.

Amazon started construction on the first phase in early 2020. That same year, it bought the development site, known as Metropolitan Park, for $155M from JBG Smith, the same REIT it leased the short-term offices from and partnered with on the development.

It also acquired the Phase 2 development site, known as Pen Place, for $198M last summer. In March, the company said it was pausing the development process for the second phase, but it said Monday it remains committed to completing the $2.5B investment and creating the 25,000 jobs it promised.

The company is slated to receive $750M in financial incentives from Virginia and $23M from Arlington County, contingent on creating the jobs it announced when it selected the site in November 2018.

“I’m thrilled to see Amazon's Met Park opening and Amazon’s unwavering commitment to our community," Arlington Chamber of Commerce CEO Kate Bates said in a statement. "From the beginning, Amazon has translated their promises into tangible actions."

The project has been viewed as a catalyst for the larger National Landing district that was rebranded when Amazon announced it would build its headquarters in the area between Pentagon City and Crystal City, and dozens of new restaurants and retailers have been opening in the neighborhood that could benefit from the increased activity.

Amazon's new office buildings have a series of in-house food offerings in the amenity spaces, but the company said it only designed those to handle about 30% of the building's capacity, encouraging the majority of workers to dine at nearby businesses.

The company on Monday also revealed its names for the two buildings: Jasper and Merlin. They are named after previous internal code names for two of its projects, a modernization of the Alexa application and a cloud-powered business product called Amazon QuickSight.

The buildings have four entrances for employees and 62 total elevators. They have four levels of below-grade parking, including 290 electric vehicle charging stations and 620 bike racks.

Their outdoor amenity spaces include two rooftop dog parks, two event terraces, two café areas, one garden area, an urban farm and an outdoor kitchen. The development also features a 2.5-acre outdoor public park with a dog park, a children's play area, a community garden and art installations.

On the ground level, the buildings have 50K SF of retail leased to 14 local businesses, including a bike shop, dog daycare, fitness club, early childhood education center, art studio and several other restaurants and retailers.

More than 7,800 workers participated in the project's construction, 96% of whom were local, Amazon said. It said more than 400 local firms received contract awards for the project, making up 88% of the total contracts, and 78 contractors were small or diverse businesses.

"This project is extraordinary in many respects," Arlington County Board Chair Christian Dorsey said in the release. "It will bring us significantly closer to fulfilling the community's vision of Arlington and National Landing as an urban neighborhood with a better balance of office, residential, and retail development, more and better public spaces, and more and better access for pedestrians and cyclists."