Introducing the Sky House at 150 Nassau Street, a true one-of-one masterpiece. The brainchild of architect David Hotson and interior designer Ghislaine Vias, Sky House is as much a home as it is an immersive art piece. Named twice by Interior Design Magazine as the best of the best – in 2015, as best of the decade, and in 2025 as best of the last twenty years – Sky House outshines its peers precisely because it has none. Every detail has been mathematically engineered for precision, and meticulously maintained since its completion. This was no small feat; the planning and construction took over 5 years. The result was worth the wait. Spanning the top four floors of the American Tract Society building – including the full, two-story arcade – Sky House sprawls playfully and deliberately across its 6,500 square feet of interiors. One must first discuss the slide: a two-part spiralizing vortex made of German stainless steel. It launches from the top floor – the acute apex of the building – and plunges through to the next floor. Take a moment to catch your breath, then descend the second section, a vortex that releases giddily into the foyer. Here, on the main level, you begin to appreciate the scale of the home. It is a grand, open space, where immense arched windows provide 270-degree views, including both rivers and skyline landmarks. Cutouts, partitions, and viewing decks allow the ceilings to vault up nearly 46 feet to the top of the building. The volume of space allows for a functional rock wall and a rope swing to grace the middle of the room. Sunrises and sunsets cast unobstructed light across the floor, which opens to a 1,200 square foot terrace to the east. Here, you’ll notice the pedigree of the building itself, which dates back to 1895. The green pitched roof, copper portholes, and 20-foot-tall caryatids contrast the ultra-modern finishes and textures from the interior. The home is also undoubtedly practical. The kitchen includes a large island, providing ample counter space, and includes a top-of-the-line appliance package by Sub-Zero, Gaggenau, and Miele. Behind it, a secondary prep kitchen is perfect for caterers or major holidays. There are two wine refrigerators on this floor – each Sub-Zero – along with a full laundry room, two powder rooms, and walk-in coat closet. If you look closely, you’ll find a hidden pantry behind a column's face, and storage below sections of the living room floor (a convenient byproduct of having the floors raised so that the windows sit more perfectly at eye level). On the south end of the floor is the primary suite, which includes exposures to the south, east, and west. Enter through a media or sitting room, where the snaking slide sits as visual centerpiece. The bedroom features custom wallpaper and has a corner exposure. The primary bathroom has a standalone tub with jets, water closet, steam shower, and heated nanoglass floors, as well as vanities on either end of the room. Multiple closets and a hidden room allow for more than enough storage. And there is a secluded loft bed, accessible by built-in ladder, that becomes a secret hideaway. Ascend the staircase to the mezzanine floor (look up as you go to see the intricacies of the architecture). A catwalk overlooking the lower level leads to a study, ideal for work or for appreciating the magnitude of the home below. (One may also access this level via a covered ladder adjacent to the kitchen). The third floor contains three additional bedrooms, plus a floating lounge area. Alternate between walking on white nanoglass – an extremely hard, synthetic stone – and reinforced glass cutouts. The first bedroom faces south and west and includes an en-suite bathroom and a separate vestibule office space. The next two bedrooms each have large west-facing windows and cutouts that reveal the floors below. They share a full bathroom across the hall (peek through the shower for a clear view to the north, and look behind the medicine c