Haus Wittgenstein, also known as the Stonborough House and the Wittgenstein House) is a house in the modernist style designed and built on the Kundmanngasse, Vienna, by the Austrian architect Paul Engelmann and the Austrian philosopher Ludwig Wittgenstein. In November 1925, Wittgenstein's sister Margaret Stonborough-Wittgenstein commissioned Engelmann to design and build a large town house. Wittgenstein showed a great interest in the project and in Engelmann's plans, and spent at least two years designing various aspects of the house, including the doors, door knobs, windows, and radiators. Describing the work, Ludwig's eldest sister, Hermine, wrote: "Even though I admired the house very much, I always knew that I neither wanted to, nor could, live in it myself. It seemed indeed to be much more a dwelling for the gods than for a small mortal like me". It was owned by Thomas Stonborough, son of Margaret until 1968. For two years after this the house was under threat of demolition. It was saved after a campaign by Bernard Leitner in 1971, and since 1975 has housed the Bulgarian Cultural Institute.