By default, Place of Interest data is rendered as textured cube by demo app. If you want to customize this, check poi builder in demo app. You may replace default implementation with more complex. In future, there are plans to start adding specific builders for specific poi (e.g. builder for cache machine, street lights, etc.)
http://wiki.openstreetmap.org/wiki/Simple_3D_buildings
In short, all complex buildings are defined via multiple simple polygons with height, height under ground, colors, etc.
For example, you can check how Saint Basils Cathedral is defined (take a look at Members list):
https://openstreetmap.org/relation/3224486