Cromlech of Almendres
Located in the Alentejo region around Evora, the Cromlech of Almendres is the largest of about 100 such megalithic monuments on the Iberian peninsula. Built around 7,000 years ago — or about 1,500 to 2,500 years before Stonehenge in England — the cromlech was used for various purposes, including as an observatory to mark the equinoxes and solstices of the sun as well as the movement of the moon. Shallow base relief carvings on a number of the stones have led archeologists to speculate that some of the stones may have represented various deities associated with heavenly bodies. No one can say for sure, however, since the cromlech was built long before the invention of writing. Originally the stones were placed in a horseshoe arrangement facing the direction of the rising sun on the summer solstice, but many other stones were added in subsequent years to yield a much more complex astronomical instrument.