Seattle’s tech boom has come with some... interesting amenities. As dog runs and fancier communal kitchens have become commonplace, buildings fight to stand out with features like rooftop chicken coops and herb gardens. It’s especially pronounced in South Lake Union, a popular hub for Seattle’s new influx of tech workers. AMLI Arc, for example, scrapped plans for a shared recording studio, but does offer lockers designed especially for outdoor gear. Marina SLU has a two-lane bowling alley. Leeward has an arcade.

Then there’s Sitka, a Vulcan-developed apartment building that opened in South Lake Union late last year, which has a shared treehouse—kind of like the standard resident lounge, but cozier and up in the air.

Designer Daniel Mihalyo of Lead Pencil Studio calls it the “Island Treehouse” after two influences: The “informal architecture of Northwest treehouses” and “a cross section of a San Juan Island outcropping.”

While the thing is already built (Sitka opened its doors in November 2018), it’s kind of a work in progress: A green roof will eventually be home to ferns, moss, and other small plants. And strictly, it’s more of a pillar-house, since it’s not built in a tree. Still, said Mihalyo, it’s meant to “beckon as an alluring space within the tree canopy” below—at least, once all the courtyard’s evergreen trees grow up a little more.

Inside, it’s a more condensed and cabin-like version of the resident lounge, with a wood stove, a wet bar, and booth seating. Wood paneling covers every surface, like a more high-design backyard treehouse. Both the unconventional roofline and a gable define the shape of the interior.

On one side, a hexagonal door lets visitors in from a catwalk. On the other, double wooden doors transform it into a semi-outdoor space.

“The island treehouse is intended as an intimate retreat for residents to socialize, relax and converse with one another in a rustic space among the forest canopy,” said Mihalyo.

Just as it’s not the first over-the-top amenity to be introduced by a Seattle luxury apartment complex, it’s also not the first time a developer’s gone to extreme lengths to integrate Seattle’s woodland vibe into a more stark landscape of modern architecture. Back in 2017, Security Properties chose to style the rooftop terrace at the Kinects apartment building in the Denny Triangle as a mountaintop—complete with an 18-foot hemlock tree, lifted by crane to the 41st story.

But living in a developed South Lake Union forest doesn’t come cheap. Market-rate rent at Sitka ranges from $2,020 to $5,640 a month—although 77 units have more affordable rent through Seattle’s MFTE program.

This article has been updated to better reflect Sitka’s selection of apartments.