Completed in 2005, this piglet-pink building with trees growing from its facade and meadows sprouting on its rooftops was the final design of Viennese artist Friedensreich Hundertwasser. It reflects his philosophy of creating unique spaces in harmony with nature, an ‘oasis for humanity’. Inside are offices, flats and shops, as well as a small hotel and a cafe. If you understand German, join the one-hour guided tours to learn more about the man and his intriguing vision.