The satellite image of the US capitol building in Washington DC has been modified to hide the details.
The below url should show both modified and clear neighboring tiles. These are not lower resolution images, but digitally altered images like what is sometimes done to hide faces.

http://maps.google.com/maps?q=washington+dc&ll=38.889831,-77.011424&spn=0.004613,0.007939&t=k&hl=en

Are there any other modified map locations?

What could the reason for this be?
It is publicly know that the capitol building is located there and what its normal appearance should be. This doesn't seem to be protecting anything.

George

The whitehouse has also been edited, along with several other sensitive locations in the DC area. This is standard practice with public satellite imagery.

http://maps.google.com/maps?q=whitehouse,washington+dc&ll=38.897610,-77.036669&spn=0.005139,0.007918&t=k&hl=en

The whitehouse editing is less obvious – the top of the building has been blanked out, and foliage has been added to obscure the details of the surrounding land.