This is a piece of image I got from SinGeo, which shows that many parts of Singapore maps are deliberately covered up by Singapore Street Directory. One of them was the Istana. What are the rest? If you ask me, I would guess it might be military bases, including some of the ultra sensitive one like, howitzers, missile, navy battle ship and some aircraft deployment. Your guess is as good as mine.
I also can say, Singapore Street Directory WILL NOT confirm this. (Link)
Update: From SinGeo Blog,
recent updates and improvements to the satellite imagery of Singapore in Google Earth have been replaced with older imagery.... (Link)
I wonder, is this some kind of cover up by Google Singapore for security purposes....
if my blog got 10'000 hits daily, they may require to clear this up. I guess not now.