12 of the World’s Most Mysterious Monuments & Ruins

Stonehenge

Perhaps the world’s best known monument is Stonehenge, located in the English county of Wiltshire. It’s composed of earthworks surrounding a circular setting of large standing stones and is believed to have been built around 2500 BC but has been revised and remodeled over a period of more than 1400 years. Though theories and speculation abound, no one knows what the original purpose of the prehistoric monument was and it remains one of the earth’s greatest mysteries.