I really liked the Flat Earth series that was like 6 hours long. It went into tons of neat things like Starbases and old architecture along with the free power Tesla idea, etc...

Some other neat conspiracy videos I've watched have been things on the World Fairs, the Mud Floods, Cabbage Patch Babies, and mountains are actually petrified giants.

Anyone know of any other cool conspiracy rabbit holes to go down that require a little imagination and are entertaining similar to the one's I've listed?