In April 2015, then-Expedia Group CEO Dara Khosrowshahi stood beside Ed Murray, the Seattle mayor at the time, and gleefully shared the first details of Expedia’s surprising and ambitious plan: to uproot its headquarters from its longtime home of Bellevue, Wash., in favor of a potentially iconic waterfront Seattle campus.

Four years later, both of those leaders are long gone — but the project stayed on course and is finally close to completion.

With CEO Mark Okerstrom now at the helm, Expedia has charged ahead on the HQ move. On Wednesday, just a few months before employees arrive, the company opened the doors of the $900 million campus to media and Jenny Durkan, the current Seattle mayor.

The first Expedia workers will descend on the campus in October, and they will come in waves of a couple hundred at a time through next summer when all the space under construction is complete. When Expedia is done renovating several existing buildings on the former campus to biotech giant Amgen and adds two new ones, the site will be able to house all 4,500 of Expedia’s Seattle-area workers. Expedia has the approval to continue building out the campus, and it could eventually house more than 8,000 workers.

For Expedia employees, the new HQ is not only located a new city, 12 miles west of its existing Bellevue campus across Lake Washington. It’s a totally different environment — a sprawling space with stunning waterfront views in the Interbay neighborhood of Seattle.

“I don’t think there’s an urban campus like this in America that I’ve seen,” Durkan said. “I also think it shows the amazing vitality of Seattle. You’ve got Amazon that has a very urban campus building base and Expedia, which is going to have this amazing campus that pulls in the environment around it, and then you see everything in between.”

This is the second time this week Durkan has made an appearance to celebrate the expansion of a global tech giant in Seattle. On Monday, she welcomed Apple and that tech giant’s plans for a significant expansion in the city that could see it grow to more than 2,000 Seattle workers in a few years.

Apple’s expansion, the new Expedia complex and a big new campus for Google will bring thousands of workers to an already heavily congested part of Seattle over the next few years. Expedia is working on a number of solutions to the impending traffic crunch, including a shuttle service, vanpools and what one Expedia official called one of the biggest bike storage facilities in a corporate office.

Expedia will also put money in the pockets of employees who don’t drive to work — $5 per day.

The city of Seattle has been “embedded” with Expedia for years in figuring out how to mitigate traffic impacts, Durkan said. While she didn’t give specifics, Durkan said the city and Expedia are working with King County Metro to possibly add bus service as well as other options.

A big part of the city’s plan to reduce traffic revolves around housing. Durkan said the city will unveil some new policies this summer to help build more affordable housing in the city.

“One of the first things we have to do is make sure we have housing close to where people work, because the closer housing is to work, the less people are going to get in their single occupancy vehicle,” Durkan said.

Expedia officials boasted how few people drive solo to work today. Only 38 percent of Expedia workers drive to the current Bellevue offices alone.

When the new campus opens, Expedia expects that number to jump to nearly 50 percent. But as the dust settles on the move, Expedia leaders are confident they can drive down the number of people commuting alone in cars to less than 30 percent.

With just a few months before the move, the campus is very much a work in progress. Crews are still renovating the existing buildings to build open floors for Expedia, as well as a wealth of common areas. Expedia is dedicating close to two acres of the campus to public space, including a new beach park and rebuilding part of a pedestrian and bike path through the campus to transport people all the way across Seattle’s waterfront.

The new campus will feature “biophilic design,” which involves connecting people and nature to increase physical and mental well-being through views of the water, mountains and open office spaces with plenty of natural light. Expedia plans several acres of outdoor spaces including playing fields, meeting spaces and an amphitheater that will have WiFi and enhanced mobile data.

In the middle of the campus is a centerpiece mixed-use building akin to the Amazon Spheres called the Prow. A prow is the forward-most part of a ship’s bow that cuts through the water. The structure, though still in the early part of construction, definitely has the look of a ship.

On the edge of campus, close to the water, will be a building for larger team meetings that is partially underground. With a grass-covered roof that helps burrow the building into the hillside, the building is meant to feel more secluded than the rest of the campus.

Expedia first announced plans to move from Bellevue to Seattle in 2015, paying Amgen $229 million for the campus on Elliott Bay.