Late last week, Google released an update to the 3D Buildings layer in Google Earth. If you turn the layer on, and fly to “Helsinki, Finland” they have also added most of the city with 3D Building models with photo-realistic textures.
This adds to the growing list of cities which Google has added to the Google Earth layers with 3D buildings. Google has not released any details on how the cities were modeled. But, I suspect they are using data from a variety of sources using techniques such as photogrammetry from aerial photos, possible use of Lidar data and photos from Street View, and licensing data from various 3D city modeling firms. Here is a list of recent posts summarizing cities added to the 3D Buildings layer.