These models are specifically for the new free Google Earth 4 (beta) and utilize texture mapping to add a great deal of realism to the scene. Texture maps are photos applied to 3D models so you can add great detail without slowing down the 3D rendering in the application. Done right, the models blend in with the surrounding aerial photography and look excellent viewed at all angles. However, the models can be larger files due to the additional picture data. So, they may take a bit longer to download (although probably not as much if you tried to render all that detail geometrically).
The first model was done by Planet 9 Studios and can be found on their demo page here. They have created an excellent model of the San Francisco famed Transamerica tower and the surrounding neighborhood. If you have Google Earth 4 Beta download the file here 
(1.6 Mbytes). [If you are using GE 3 you will see nothing when it loads.] Make sure you…
Make sure you zoom in to the base of the tower where you can see the details of the structure and photos of the windows at the street level. You can also see the street level windows of the nearby stores and buildings. A beautiful model.
Another excellent 3D model is the Kings College Chapel in Cambridge, England (3.7MBytes – GE 4 only). This model combines good geometric 3D detail with carefully done textures. It was developed and posted at the Google Earth Community by someone called ‘barnabu’.
About Frank Taylor
Frank Taylor started the Google Earth Blog in July, 2005 shortly after Google Earth was first released. He has worked with 3D computer graphics and VR for many years and was very impressed with this exciting product. Frank completed a 5.5 year circumnavigation of the earth by sailboat in June 2015 which you can read about at Tahina Expedition, and is a licensed pilot, backpacker, diver, and photographer.