The High Line-an elevated freight track in Lower Manhattan transformed into a linear park-offers rustic illusions and thrilling views of the city. Eventually, it may be walled in by generic blocks, but for now the panorama - from the Empire State Building across the low-rise blocks of Chelsea and the West Village and down to the harbor - has few interruptions. Jean Nouvel and Frank Gehry make fleeting appearances on the Westside Highway. The one significant neighbor is HL 23, a 14-story condo block sheathed in glass and steel, swelling out over the park. It’s the first ground-up building by NMDA, Neil M. Denari’s Los Angeles-based office, and it demonstrates how New York’s tough zoning code can be waived to advantage. “It’s easier to break out of the box in the Wild West of Manhattan”, says Denari. “This is still unsettled territory, with large warehouses and few residents to raise objections”. That will soon change as the area gentrifies, but two first-time developers seized their chance to exploit a tiny site alongside the High Line before the park opened, and commissioned NMDA to design something radically new. In spring 2005, the architects produced thirty schemes in six weeks, pushing the envelope to create a block that would have an elegant signature, while maximizing square footage and relating harmoniously to the park. “It had to fit in and stand out”, explains Denari. “The design was developed from the inside out, in an accumulation of small negotiated moves. We wanted the form to be a continuous surface rather than the conventional wedding cake with set-back floors”. In fact, it’s stepped out and back; with the top that is cantilevered 1,5 meters over the park to the east, and again to the south over a spur in the tracks. That sculptured form was submitted to the city planning department for prior approval, and they granted seven of eight requested waivers in the hope that this block would set a benchmark for future development. Such a complicated building takes time to prepare and construct. Two years were required to secure all the permits and locate manufacturers who could meet precise specifications within the budget. It’s a sad comment on the decline of American manufacturing that nearly all the elements had to be sourced abroad. The large triple-glazed façade panels with slender stainless mullions were imported from China, the structural steel from Canada, the ribbed steel fascia from Argentina, and the black anodized aluminum that conceals the rooftop services from the UK. Unforseen delays and a quest for perfection prolonged construction over four years, but the developers - Alf Naman and Garrett Heher - held firm. Most New York residential buildings have concrete frames; HL 23 uses steel to support the cantilevers. “I like to work with structure rather than design images and then reverse engineer them”, says Denari. The peripheral cage of steel beams is fully exposed and protected with fire-resistant paint. To dramatize their presence the diagonals extend through three or four stories, and the concrete floor plates are exceptionally thin, making the building appear taller and lighter. A ceramic frit projects the structure onto the curtain walls so that the diagonals are visible from the outside even when the motorized window shades are lowered for privacy or sun control. Each fritted outline is different and the corners are rounded to soften the sharp angles. That gives the façade a depth and a dynamic quality to which the eyes and the body react. The client considered eliminating this feature to save $180,000, but, realizing how bland the curtain wall would look without, agreed to keep it. The fluid profile is enhanced by the play of light across the east wall, which is clad in molded bead-blasted steel panels. They were fabricated by a firm in Buenos Aires. There are four patterns, configured differently to suggest greater diversity-a strategy that Gehry pursued in his Beekman tower. Here, in a building that is a fifth the height, the surface relief is shallower and the effect more refined. It suggests a sensuous, firm-bodied woman in a silk dress that ripples in the breeze. To continue the analogy: her skirt is slit up the side, and this break in the east façade accommodates a narrow window that complements the curtain wall. HL 23 plays off the raw industrial frame of the High Line and it provides a cinematic experience as one approaches and walks past. Denari jokes that the building was photographed so often, even before completion, that it should soon take its place as one of New York’s landmarks and be included among the postcards sold in Times Square. Luxury resides in the volumes and natural light of this building, as well as the materials and precision of the detailing. In the all-white lobby, Denari and project designer Stefano Paiocchi designed a cantilevered reception desk that was hand-carved from a single block of marble by an Italian sculptor. There’s a two-story maisonette with a private garden at the base and a duplex penthouse with an upper level room that opens through glass sliders to a wrap-around terrace. Each of the nine apartments in between occupies a floor and is subtly different in plan and height. Thomas Juul-Hansen, a New York based Danish architect who formerly worked with Richard Meier, designed the minimalist interiors with their oak floors and figured marble bathrooms. But, to a greater degree than in most upscale condos, it’s the architecture that counts. The angled planes of glass frame the sky, distant towers and the foreground of water tanks, as well as the lush plantings along the High Line. Inside and outside are as one; residents and outsiders share a private monument that helps shape the public realm. “Making it pencil out was essential,” admits Denari. “A building within the permitted envelope would have been 7.5 x 21,5 meters and would not have worked financially. But we also wanted to see if we could change the market for this kind of building and have a broader impact on the city”. New York is full of giraffe-neck towers that exploit air rights to exceed customary floor-to-height ratios - a exaggerated example has risen on Madison Square, six blocks to the east. HL 23 goes the other way. Its proportions are intimate and urbane. It challenges the tyranny of the grid and the relentless orthogonality of conventional development. One wonders how many other clients will make the effort to match this achievement.