1) Ancient Egyptian pyramid 2) Egyptian artefact type 
A pyramidion (plural pyramidia) is the uppermost piece or capstone of an Egyptian pyramid in archaeological parlance. They were called benbenet in the Ancient Egyptian language, which associated the pyramid as a whole with the sacred benben stone. In Egypt`s Old Kingdom, pyramidia were generally made of diorite, granite, or fine limestone, which ....
• (n.) The small pyramid which crowns or completes an obelisk.
Pyr`a·mid'i·on noun ; plural Pyramidia . [ New Latin , from Latin pyramis . See Pyramid .] The small pyramid which crowns or completes an obelisk. 
Capstone of a pyramid or the top of an obelisk. The pyramidion was decorated and became a symbolic object that was the focal point of the small brick pyramids of private tombs.
a miniature pyramid, as at the apex of an obelisk.