Amphipolis doesn't seem likely for a Macedonian royal burial--it wasn't originally Macedonian (it was founded by the Athenians in 437 and became a Macedonian possession only during the reign of Philip II). It's well to the east of the heartland of the Macedonian kingdom. The historian Thucydides, an Athenian general at the time, was exiled because he failed to prevent the Spartans from taking Amphipolis in the winter of 424/423.
Thanks, that is some great information.
I was a Classics major for a while and have to admit that I did not know that was why Thucydides was exiled.