Back in 2016, a unicorn landed on the counter of Los Angeles’s Department of Building and Safety, an unexpected, improbable, apparently fringe project that took new eyes to see. Architectural anomalies seldom make it past the door at the LADBS, but here was the 50-story Gateway, made up of stacked buildings with funky facades: twin 20-story residential towers rested on a big, 15-story hotel block, and they supported a block of luxury apartments above, itself surmounted by an architectural asteroid from a faraway galaxy.

Usually, high-rise buildings are cautious, well-behaved point towers straight out of Euclid that rise in a single leap from base to top, their facades as pin-striped as the suits of the bankers who finance them. This was not that.

Unusual circumstances produced this unusual submission. Designed by the Los Angeles office of Gensler Architects, it was one of several projects submitted by developers panicked by an impending legislative change that threatened to downzone, and devalue, their real estate in or near Downtown Los Angeles. The site of the unicorn, north of the Santa Monica and east of the Harbor Freeway, was loaded with potential, since the critical mass of a huge high-rise could redefine the area and create its own real estate value.

This article appears in the Fall 2022 issue of Alta Journal.

Scrambling to get in under the wire, before the downzoning passed, developers hired architects to create “placeholder” designs meant to win entitlements (the right to build). Architects quickly put together projects, designing for density even if the likelihood of their being built as designed was sketchy. The upside of the real estate thought exercise was that circumstances lifted the onus of plausibility, encouraging speculation of an architectural sort in a building type usually straitjacketed by value engineering.

If the Gateway was a broad-strokes idea, the details yet to be resolved, it was brilliant in concept, a breakthrough original enough to move the architectural needle in Los Angeles and even shift the paradigm of what a high-rise in the United States could be.

It was larger than a building, edging toward urban design. Megabuildings have the potential to become self-contained cities: what Gensler was proposing was stacking and compressing three or four diverse urban blocks of Downtown Los Angeles into a building of buildings. The composite structure verticalized the idea of several largely horizontal Los Angeles neighborhoods, combining all their sociology and functions into a stack of mixed-income neighborhoods. Each building within the cluster expressed its own character, whether a hotel or market-rate housing or luxury digs.

In the 1930s, modernist sculptors took a great leap forward when they started piercing a clay or bronze mass with a void, introducing the notion of space into the solid. Now, decades later, architects were proposing the same, breaking down a building into parts that introduced voids into monolithic blocks. The openings meant that light, air, and space traveled through the building and that the roofs of some sections became the ground for others: you could go outside on the 20th floor for sun, coffee, and a chat or a swim; birds could fly in for a breather. The ground rose into the sky, bringing the environment, not to mention the community and neighborhoods, into the body of the building. Southern California’s climate would encourage designs for indoor-outdoor living that were already underway.

Residential styles imported to L.A. from the East Coast at the turn of the last century didn’t acknowledge that winter-defensive houses had migrated to a Mediterranean climate, but eventually, architects got the memo, and Victorian piles sprouted generous verandas; Craftsman bungalows, sleeping porches. Starting with R.M. Schindler and Richard Neutra, modernists introduced the idea of indoor-outdoor living. A hundred years later, at the counter of L.A.’s building department, Gensler’s unicorn was doing the same, opening the closed form of the high-rise imported from back East with multiple rooftop terraces that embraced the out-of-doors.

As unusual as the Gateway might have seemed to incredulous inspectors in L.A., the time had come, or was coming, for the new paradigm: Segmented sky cities, proposed and built, had already been surfacing elsewhere in other practices, mostly outside the United States. So why not here?


In Hong Kong in 2012, the New York firm Kohn Pedersen Fox had already developed the idea in a packed urban center, though for environmental rather than zoning reasons. In one of the densest agglomerations on earth, the developer of Hysan Place, an office building and shopping center, wanted to build a sustainable form that would flow cooling breezes through the body of the building to air-condition the surrounding urban canyon, where walls of buildings immobilized the tropical air. KPF architects Robert Whitlock and William Louie, with Bruce Fisher, pulled the 36-story, 716,000-square-foot mixed-use structure apart, segmenting it into a shopping center at the base with separate, stacked office blocks above. The individual blocks created sky gardens.

Whitlock followed up his Hong Kong success in Singapore on Robinson Road, where he cleaved the base of an elegantly faceted crystalline glass tower with a gash of landscape on rising terraces that created a spiraling oasis of greenery 10 stories up into the 30-story office building. The architect chamfered the base of the tower according to the arc of the sun to maximize daylight reaching the roof terraces. The resulting mid-rise park gave employees access to outdoor spaces and reduced the heat-island effect, in which hard surfaces like concrete and dark glass absorb radiation from the sun. Opening the usually closed skyscraper form imported into the body of the building Singapore’s character as a garden city.

“It’s important for employees to have access to outdoor spaces—they’re no longer working in their father’s office building,” says Whitlock. “Developers are pushing for wellness ratings, and that means breaking the extruded box so that each use gets its own ground floor and an outdoor connection.” He adds that as buildings get taller, breaking form structurally helps offset increased wind loads.

“I’m seeing a lot of porosity in taller buildings of large-scale projects,” says William Pedersen, a founding director of KPF. “There’s a growing acceptance among both developers and tenants for allowing nature to penetrate into the building. Tenants like it, and developers find offices with outdoor space highly marketable. There’s more potential for a building to become a city within a city. The development bodes well for the tall building.”

In 2011, KPF took the idea to an extreme in a concept proposal for a super-tall complex of stacked towers, Tokyo Grand Design. The architects basically split the bulk of a single massive tower into skinnier towers standing atop one another in three vertiginously tall piles that were themselves connected by landscaped bridges. Separations and displacements of each vertical block allowed sun, air, and view into the voids. Terraces populated even the upper reaches, but at the base, the towers transformed into an alluvial fan of greenery, creating a vast urban park serving the whole building and the surrounding neighborhood.

Southeast Asia has been receptive to sky cities. More than 50 years ago, Japanese architects conceived megastructures to float above cities, but no one thought these imaginative shock-and-awe provocations would ever be built. Proposals smaller than the Tokyo Grand Design have actually been built, and rather than hovering over cities like the megastructures of a previous generation, they are rooted in the street grids of existing urban fabric, and they involve conventional rather than exotic construction and engineering.

The brilliant New York architect Paul Rudolph, who died in 1997, did build what in retrospect might be considered forerunners of the current crop of segmented buildings, all outside the United States. An admirer of Frank Lloyd Wright, who broke the box horizontally to work the building into the landscape, Rudolph instead broke the vertical box to bring the building into the sky and the out-of-doors into the tower. In several Singapore projects, built and unbuilt, he fanned and terraced low-rise buildings out from the base of a tower (as at the Concourse on Beach Road), or he perforated the building’s skin into three-dimensional honeycombs of terraces (as at the Colonnade). In the 1979 project Marina Centre, a virtuoso design, he bridged open spaces with apartment blocks and separated towers from one another and from their bases, multiplying outdoor decks.

The American master never built his 1990 Gatot Subroto condominium complex of eight towers in Jakarta, which featured three-story blocks pinwheeling outward, each block leaving void decks between it and the next (the outdoor sky gardens added up to more than the footprint of the whole site).

But 17 years later in Singapore, Ole Scheeren, a German architect with offices in Beijing, Hong Kong, Berlin, and Bangkok, proved Rudolph’s Jakarta proposal practicable at the Interlace, a vast complex of 31 apartment blocks containing more than 1,000 units. Each six-story block is elevated, some atop others, liberating the ground or rooftops beneath for outdoor space. Scheeren spun the blocks off the orthogonal in dynamic hexagonal patterns that shape large-scale open courtyards at many levels.

Applying the idea of segmentation to a point tower in Bangkok in 2016, Scheeren pixelated parts of the tubular, 78-story, mixed-use structure, King Power Mahanakhon. Cubes pop into or out of an otherwise regular high-rise tube in staccato rhythms. Last year, the City of Vancouver approved construction of Scheeren’s Fifteen Fifteen, a 42-floor, omnidirectional condominium tower with apartments projecting like cannons out from the body of the building, their roofs forming the terraces for the apartments above.


Scheeren is a graduate of what might be called the Rem Koolhaas Academy of Young Turks, and several other alumni have pursued a strategy of stacking buildings. In a graphic application of the idea to the Mirador, a huge, 21-story residential building completed in 2005 in Madrid, Jacob van Rijs and Winy Maas of the Dutch firm MVRDV textured and color-coded a massive, conventional apartment block, distinguishing numerous different “neighborhoods” within an architectural collage that attacked the modernist idea of standardization. The architects then stacked separate blocks atop the block, leaving a large semipublic outdoor space between them.

In 2005, Joshua Prince-Ramus of Rex, a Koolhaas grad based in New York, proposed the spectacular riverside Museum Plaza in Louisville, Kentucky, a stack of six towers and blocks that all look like the Seagram Building, by Mies van der Rohe, buttressed by a truss set on the oblique. In 2012, Bjarke Ingels of Big—based primarily in Copenhagen and New York—proposed an even more startling vision of stacked buildings in Seoul, configured like a monumental three-dimensional tic-tac-toe board, a city in the sky.

These projects owe a major conceptual debt to Koolhaas’s Hyperbuilding, a self-contained, one-kilometer-tall megastructure imagined in 1996 as a “test” for the next urban step for a city of 120,000 on a site in Bangkok. Eliminating the commute that has choked flat urban grids, he proposed that an entire vertical city—residential, medical, retail, educational, and cultural spaces, all connected with cable cars, gondolas, and high- and low-speed elevators running on a diagonal—be built within its armature of columnar towers. Entire buildings hung from habitable, soccer-field-size platforms that acted as parks with 12-kilometer-long promenades. Hyperbuilding remains an extreme statement of the idea of “stacking” or “piling” structures while creating ground in the sky and saving ground below for nature preserves.

In Hyperbuilding, Koolhaas pushed the idea of a building of buildings to its improbable but logical extreme, and it has served as a model or inspiration for less-complex, real-world projects at a smaller scale. In Jersey City, scaling down and simplifying the vision in 2006, Koolhaas’s firm, OMA, stacked four autonomous blocks, each with a different program—apartments, hotel, artist-studio residences, gallery space—into a 52-story tower called 111 First Street. Giving each tower its own program and outdoor terrace broke the surrounding monotony of single-use towers with no outdoor space.

Gensler may have presented its unicorn to the Los Angeles building department in 2016, but it was the New York firm Cookfox Architects that actually broke ground on its version of a unicorn, One South First, the next year in Brooklyn. It’s obvious now that the design was more than a sacrificial placeholder. Anyone traveling along FDR Drive in Manhattan will spot an unusual conjoined pair of thin buildings across the East River in trendy Williamsburg. A very tall hole segments a mixed-use, 480,000-square-foot, 42-story megastructure, which combines apartments, offices, and retail in a three-part complex set on a three-story commercial podium. The city that invented the notion of a towering skyline, New York challenged its own Manhattan paradigm with a multipart building that is unique, green, elegant, and inclusive (20 percent of its residential space is reserved for affordable apartments) and that has the critical mass of a small city. Roof-decks are landscaped and usable, and the building’s a good neighbor, designed to complement a much-loved historic monument, the adaptively reused Domino Sugar refinery next door. Gensler’s unicorn may be funkier, but New York beat Los Angeles to the punch.

Plan checkers at the Los Angeles Department of Building and Safety might have blinked when they opened their computers to see the Gateway. But population statisticians predict that 68 percent of humanity will occupy cities by 2050, and sky cities may well populate our not-too-distant future. Prospecting for land in the sky makes sense as cities densify and technology and growing concentrations of capital allow and even encourage it. The beneficial irony of stacking buildings is that segmenting buildings as they climb proliferates the potential for open space and greenery, contributing to their sustainability. There is the humanistic dividend, too, of breaking down the scale of a Manhattanized world of monolithic, one-style skyscrapers into neighborhoods that allow people to escape elevators into a more pedestrian environment.

The downzoning that scared developers in Los Angeles did not come to pass, so Gensler’s unicorn will not be built. But it still stands, along with a few others that have sneaked into our skylines, as a paradigm shift that pokes big, constructive, sunny, green holes in the high-rise as we know it. The sky is the new limit.•

Joseph Giovannini, a Harvard-trained architect, was born in Lincoln Heights, a short mile from the LA River.