Architect Costas Kondylis, the prolific designer behind over 86 buildings in Manhattan, died Friday at age 78, according to The Real Deal. The cause of death has not yet been announced.

Kondylis was best known as one of Donald Trump’s closest and most frequent collaborators in New York City. He designed the 90-story Trump World Tower, formerly the world’s tallest residential structure, in Midtown East for the real estate mogul as well as the Trump International Hotel and Tower at Columbus Circle, and several buildings at Trump Place on Riverside Boulevard. While Kondylis’s extensive resume reveals a handful of projects associated with Trump, the architect’s 50 years designing in New York included countless high-rise designs for various local developers. 

Born in Central Africa, Kondylis studied in his parent’s home country of Greece before earning a graduate degree at the University of Geneva in Switzerland. After finishing his second masters at Columbia University in 1967, he began working for Davis Brody & Associates. While employed by Philip Birnbaum & Associates, he designed his first notable building, Manhattan Place Condo, in 1984. As one of the first high-rise condo projects in the city, as well as one of the few to focus on luxury design at the time, it caught the eye of Trump who was then expanding his New York building empire.

Five years later, Kondylis launched his own firm, Costas Kondylis and Partners in 1989. During this busy time in his career, he designed 65 buildings—one building every six weeks—from 2000 to 2007, TRD reported. Once the practice dissolved two decades later, Kondylis started his own firm, Kondylis Design.

It’s argued that Kondylis influenced the New York skyline more than any other architect in history. His more recent projects, Silver Towers, River Place, and Atelier, all towering residential properties, have helped shape the newly-developed far west side of Manhattan. He was largely recognized as the “developer’s architect,” a term he grew to embrace, having worked well with everyone from Silverstein Properties to Moinian Group to Vornado Realty Trust and Related Companies. Though his work was usually on time and on budget, it wasn’t highly favored by critics who saw his large-scale structures as too conventional.

Larry Silverstein told The New York Times in a 2007 interview that Kondylis’s name is almost synonymous with the city’s condominium architecture. “He designs an attractive, buildable, functional building,” he said. “If I’m going to do a residential building in New York, the most natural thing in the world is to pick up the phone and call Costas.”

Kondylis repeatedly stated that his primary goal was always to please the client. He was regarded as one of the most professional, humble, and patient architects in the business despite criticism or praise of his work. 

Kondylis died last week in his home and is survived by his two daughters, Alexia and Katherine. A service in his honor is scheduled for October.