One of the oldest symbols seen through the time of Egyptian inscriptions, The Primordial Hill, was believed to have been the initial building blocks of creation itself. As you may have noticed, this symbols is also believed to have been the inspiration for building the pyramids.
The top of this hill (named the Benben), in legend, rose out of the water during the chaotic process of creation, which offered the first ever land above sea level. This Benben stone (also known as a pyramidion) is the last stone placed at the heighest point of a pyramid.
Above, pictured, is the Benben stone from the Pyramid of Amenemhat III, which is kept at the Egyptian Museum in Cairo.