The tholos in the palace is strange, slightly crude in shape rather than a perfect circle, and clearly pre-dates the palace - yet it was important enough to leave as a heroon to Heracles and the Argead ancestors, and was probably used as their throne room.
This plan and the images from Google Earth show where it stood.
Philip II also built a tholos at Olympia with statues of his immediate family inside. The statues are long lost, but the building survives and is round, in keeping with ancestral cult buildings or the Argeads.
This is a very old photograph of the Philippeion from when it was first excavated by Curtius.
Round building. Ancestral cult. Anyone seeing a pattern here?
Then we get to Amphipolis: round building, possible family mausoleum ... same pattern.