The Giza Pyramids. The sides of the pyramids face the four cardinal
directions. There might be other astronomical alignments build into
the structure of the pyramids (No-9).
Ancient Egyptian astronomy never got very far, in fact.
The situation was different in the Hellenistic period when
Greek and Babylonian astronomical knowledge was fostered in Egypt
by the Greek speaking element.
One wonders about Vegas is 4 millennia:
Credit: Digital Imaging Project of Mary Ann Sullivan, Bluffton College; download site Digital Imaging Project's Pyramid Gallery. The download site gives more information.