The death of one of history's most enigmatic rulers—Egypt's King Tutankhamun—remains shrouded in mystery 3,300 years later.

Some mysteries may never be solved—but others are begging to be! Explore nine ancient enigmas in this episode of History Countdown.

Workers carved the 700-ton Obelisks of Luxor from a single piece of red granite.

From Egypt to Greece, explore different solutions throughout history for constructing giant structures like obelisks and temples.