I stayed for 2 nights at Helmuth's apartment. He was very quick to respond to all of my messages, and even helped me decide how best to spend my time in Vienna by giving me lots of useful tips and ideas of things to do. He let me check in as soon as I landed, and was a great host, making me feel very welcome. The apartment is very close to the centre of Vienna, and very easy to reach by subway. I'd definitely recommend his stay to anyone who's thinking about it!