Overall very satisfying experience. Karl and his flatmates are very kind and eager to help their guest. The location of the flat is its primary asset, very close to two underground (U-Bahn) stations. It is also close to the city centre, as well as to the conference centre of Vienna. The size of the room is reasonably OK for one person. Vienna is a city full of attractions, and it is preferable staying in a flat that is close to most of them. Staying at Karl's flat will make your stay in Vienna smooth and problem-free.