He worked throughout Australia and was the initiator of many influential urban design ideas such as the site for the Sydney Opera House and the pedestrianization of Queen Street. Karl lectured at the University of Queensland and the Queensland Institute of Technology in design, town planning and landscape architecture. Research carried out when he first arrived in Brisbane pioneered the field of climatic design and resulted in the 1944 publication of an influential booklet called "Subtropical Housing". He was instrumental in establishing, and was the first president of the Brisbane division of the Australian Planning Institute and the Queensland Branch of the Australian Institute of Landscape Architects and was a Fellow of the Royal Australian Institute of Architects. Karl Langer died in 1969. His funeral was held in the Chapel of St Peter's Lutheran College, Indooroopilly, which he had designed. He was cremated at the Mount Thompson Crematorium where he had constructed the East Chapel. Karl Langer's work was featured in the Hot Modernism exhibition at the State Library of Queensland in 2014. State Library of Queensland also holds a large number of his architectural plans. The University of Queensland Fryer Library holds 89 boxes and around 1800 of Langer's architectural plans. He was the designer of buildings, including:  and worked in the regional centres of Queensland as an architect, town planner and landscape architect, producing these works:  He also authored a number of books, including "Sub-tropical housing", published in 1944 by the University of Queensland.