Hundertwasserhaus, a collaborative work with architect Peter Pelikan (constructed 1983-85), is an amazing residential block with 50 apartments. It is hard to imagine that this wild creation (at the corner of Lowengasse and Kegelgasse) actually houses regular tenants. The exteriors literally looks like enormous paintings or quilt works sprung into three-dimensional glory. Trees sprout from roughly rectangular window openings and the uneven balconies of the roof terraces, and the floors are designed to look and feel uneven. A fountain adds to the streetscape alongside the apartment tower. There is now a small store next to the building, capitalizing on the steady stream of visitors. A cafe on the ground floor is the only public space inside the tower. There is no access into the private apartments.

Begun in 1989 and opening in 1991, Kunst Haus Wien is a museum that was formerly a factory building for Thonet bentwood furniture (originally constructed in 1892). In keeping with the organic theme, the floor is not flat, so watch your step! Hundertwasser designed the brick pavement to be bumpy and wavy so that the walking experience is like a "melody for the feet". Irregular pieces of glass, metal, ceramic tile and wood add color and vibrancy as the new facade designs take over the original structure. The facade is the "third skin" with an irregular checkerboard of windows and treatments.

There is a store on the ground floor, and the garden cafe is a wonderful photo opportunity. Besides the colorful flowers and greenery, you can snap a few pictures of the "back" elevation of the building. The museum contains a selected review of Hundertwasser's works along with special exhibitions of modern art. The address of Kunst Haus Wien is Untere Weissgerberstrasse 13.

Hundertwasser has turned this apartment block into a lasting imprint on Vienna. The bright colours and his hatred of straight lines leads to something that you may not see the likes of ever again (and it's free!).

You are not allowed into the building so as not to disturb the residents, but looking from outside and sitting on the fountain should suffice for most.

On the other side of the street there is an arcade which houses (among tourist shops) the famous toilet, perhaps the finest in the world. It is worth the €1.50 to see what some people may consider absurd, but most genius.

Easy access from Schwedenplatz, just take the N tram a couple of stops past Radetzkyplatz. Otherwise its about a 15 minute walk from Wien Mitte Station

The Hundertwasserhaus is a must-see in Vienna. Since the house itself is a residential building, the authorities built another complex across the street in the same style to accommodate the tourists. Aside from various souvenir shops and cafes, you can find the Toilet of Modern Art in this building. It is definitely worth a visit, even if you're not in need of a bathroom!