What are the most important government buildings in a country?

Besides the headquarters of the three branches of government (ex. White house, capitol, supreme court) what other government buildings approach these three in importance? This includes the enitities which they contain as well as their physical size. ex. pentagon

DHS, FBI, CIA, Homeland Security, ATF, and many more. If you are planning an attack like other responders have mentioned, this would be the last place anyone would be asking sort of a question as yours. That is plain silly of them to say that!

Honestly it would have to be the IRS building, or the local welfare office.

sounds to me like you're plotting some sort of attack......

I AGREE!! IT DOES SOUND LIKE YOUR PLANNING AN ATTACK!! WOW!!