England: Stonehenge (completed around 1550 B.C.)
On the longest day of the year, June 21st, the sunrise solstice can be seen from between Stonehenge’s two most eastern pillars. On the shortest day of the year, December 21st, the sunset solstice can be seen from between the opposite stones.This unique alignment of stones suggests that Stonehenge was in fact an accurate calendar, which helped the ancients to keep count of seasonal cycles.
The Mayans: “pyramid serpent” at Chichen Itza (800 A.D)
This pyramid built over a millennium ago, was situated and oriented with a precision to commemorate the rising Sun on the longest day(Summer solstice). On the left hand side, the rising sun casts an undulating shadow which rises up the steps, as a snake would, and then disappears. This particular shadowing lasts seven or eight seconds and it occurs once a year. One day later, the alignment is no longer perfect and the shadow is not cast. So this astronomical landmark of an ancient culture which tracks the seasonal cycle and marks the completion of an year.