10. The Khatt Shebib
Discovered in 1948 in Jordan, this 93 mile-long mystery-wall remains a puzzle to researchers to this day. While you would think such a construction would serve a purpose, most historians can’t figure out who built it or why. Some traces of ancient agriculture have been discovered west of the wall, which has led to theories that it could have been built to separate farmland from the nomads. Sadly, there just isn’t enough evidence to come up with anything conclusive.