One of the most famous ancient Spring equinox celebrations was the Mayan sacrificial ritual by the main pyramid at Chichen Itza, Mexico.
The main pyramid – also known as El Castillo – has four staircases running from the top to the bottom of the pyramid’s faces, notorious for the bloody human sacrifices that used to take place here.
The staircases are built at a carefully calculated angle which makes it look like an enormous snake of sunlight slithers down the stairs on the day of the equinox.
The Mayan Calendar was very precise in this respect, but today the Mayan calendar is most famous for ending exactly at 11:11 UTC on the 2012 December Solstice.
Knowledge of the equinoxes and solstices is also crucial in developing dependable calendars, another thing the Mayans clearly had got the hang of.