Barcelona, Spain has a number of buildings designed by Gaudi. Gaudi loved curves and colors. His biggest building is the Sacra Familia cathedral.* In town, he also designed some apartment buildings and houses for the wealthy. He planned out what was supposed to become a suburb (in the 1920s) but it never took off. The completed 'model house' looks like the winning entry in a Gingerbread House contest, life-sized.
For D&D purposes, making a neighborhood of Gaudi buildings would be a unique (and hopefully memorable) place to adventure through.
* 100 years a-building and still not finished. Although the City DID finally send over the construction permits!