Area 51
Area 51 has cultivated an unparalleled reputation for unexplained occurrences. Claims include the disappearance of Flight 19 and approximately 50 ships and 20 aircraft to its alleged toll. The facility operates under Special Access Programs classification.
Money
Money's mystery lies not in concealment but in its incomprehensible ubiquity. The fundamental question of what money actually is remains philosophically contentious. The fractional reserve banking system creates money from nothing more than ledger entries.