High atop Fajada Butte in Chaco Canyon,

New Mexicois a 900 year old petroglyph,

known by archaeologists as

the “Sun Dagger”.

It is the only known solstice marker in the

world that uses the sun at mid-day to

mark the first day of summer.

On that day, the sunshine passes through

three huge slabs of rock to create a shaft

of light which precisely bisects

a spiral petroglyph.