The American Tract Society Building is one of the oldest surviving skyscrapers in NYC. Tucked away inside is a four-story, 6,500-foot expanse with full panoramic views of the city. It had never been inhabited, until now.

David Hotson, along with Ghislaine Viñas, made over the space as a home that’s equal parts whimsical and austere. The original arched windows and many of the original steel beams stayed intact, but the verticality has been transformed with bold, playful features. Hotson has said that he wanted to “constantly exploit the fact that we’re sitting on top of a skyscraper in Manhattan.”

And while a glance at the dizzying array of beams hanging overhead demonstrates that idea, it’s a concept taken to new heights with an 80-foot slide that snakes straight into the living room, a clear bridge that appears to float in midair, and handholds that allow you to climb a central support beam like a rock wall. If you make it part way up, you can lounge in the “nest,” an intimate nook squeezed within the structure’s girders. From there you can keep climbing to an almost attic-style space.

Of course, what you miss in these still photos are the incredible facets and “voids”–the geometric frames within frames that connect rooms like fractals. There’s some stunning camera work in the embedded video that illustrates these moments better than words can, and they reveal a level of design thinking that transcends what one might otherwise pigeonhole as an 80-foot-long gimmick.

But I mean, what a gimmick!