The world is home to a plethora of fascinating ancient ruins, from crumbling cities to temples that have withstood the test of time. Many of these ancient societies were incredibly innovative and forward thinking. Just take a look at their meticulous city planning and incredible feats of engineering; some of which we are yet to fully understand. Some of the most captivating ancient ruins are full of thousand-year-old mysteries that will boggle even the most curious of minds.