Which is the best real estate in the US?

Depends on your point of view, but usually anything unique (Empire State Building, or overlooks San Francisco Bay, or is on the top of Mt. McKinley...), so large it is controlling in some way (the King Ranch in Texas for example), or has intrinsic additional value (oil/coal/other reserves). And best could mean something like Yellowstone National Park, which is unique and irreplaceable. But then again a lot of folks think there's no place like home!!!