We all know Pyramids, the Egyptian tombs built to preserve dead bodies (mummies) of the Egyptian rulers or pharaohs.
In ancient days people treated Egyptian kings as divine people who were directly appointed by Gods to rule them. In respect to their royalty they were mummified and buried with some treasure after death.
Why triangular pyramids?
Pyramid is derived from the word Pyramis which is a wheat cake with pointed top. Pyramid of Djoser is the oldest pyramid which was built during 2630 BC–2611 BC.
Initially they constructed pyramids in stepped style. Later they constructed with smooth triangular sides. These sides represent sun rays and from the base it points to the sky. They were constructed facing west. So that when sun sets, rays pass to the top. This creates a passage for the pharaohs to reach afterlife/heaven.
This reminds of a scene in an Hollywood movie called Gods of Egypt in which after death the soul travels through a passage and reaches a door where it has to offer valuable things to reach afterlife. That’s why Egyptians buried many valuable things along with the mummy so that the soul offers them to the guardians of the heaven to allow them to pass through afterlife.
On the other hand modern civil engineers or architects say conical structures are the strongest in architectures in the world. They can withstand strong winds or natural disasters like earthquakes.
That said pyramids are triangular tombs pointing to the sky to allow the spirit to pass through afterlife or heaven and to withstand all the natural disasters.