Google Earth User Guide - Manual (Page 37)

you see only major boundaries. When you zoom in to a more confined
region, you might see state or county labels depending upon your viewing
elevation.
Viewing 3D Buildings
Some geographic areas in Google Earth database display simple 3D
buildings. To view these:
1. Turn on the 3D building layer by selecting the 3D Buildings folder
check box in the Layers tab.
2. Position the viewer within a reasonable viewing altitude over a major
city such as San Francisco. Some 3D buildings start to appear from
an eye-elevation of 10,000 to 12,000 feet. Check the eye-elevation
meter on the lower right of the 3D viewer to determine your current
viewing height. The 3D buildings appear as light grey objects over the
imagery of the city.
3. As you zoom in, more details will appear until you can see the entire
shape of a building.
4. Use the tilt and rotate navigation tools to get the best view of the
buildings.