While widely known for his the poetic sensibilities of his spaces, Kahn also worked closely with engineers and contractors on his buildings. The results often were technically innovative and highly refined. In addition to the influence Kahn's more well-known work has on contemporary architects (such as Muzharul Islam, Tadao Ando), some of his work (especially the unbuilt City Tower Project) became very influential among the high-tech architects of the late twentieth century (such as Renzo Piano, who worked in Kahn's office, Richard Rogers, and Norman Foster). His prominent apprentices include Muzharul Islam, Moshe Safdie, Robert Venturi, Jack Diamond, and Charles Dagit.