Exterior, Flat RoofLine, Concrete Siding Material, and House Building Type Considered Wright’s greatest public building in his Chicago years, the Oak Park Unity Temple (constructed 1906-1909) is a massive structure built entirely of reinforced concrete, which he deliberately left exposed in accordance with the architect’s philosophy of organic architecture. 
  Photo 1 of 8 in 8 Frank Lloyd Wright Buildings Inducted Into the UNESCO World Heritage List

8 Frank Lloyd Wright Buildings Inducted Into the UNESCO World Heritage List

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Considered Wright’s greatest public building in his Chicago years, the Oak Park Unity Temple (constructed 1906-1909) is a massive structure built entirely of reinforced concrete, which he deliberately left exposed in accordance with the architect’s philosophy of organic architecture.