The Temple of Solomon in ancient Jerusalem was destroyed by the Babylonians in the year 586 B.C.E. It's said that the Ark of the Covenant, a chest containing the stone tablets Moses brought down from Mount Sinai, resided in this place of worship before the invasion. The question of what happened to the Ark is one of the biggest mysteries in biblical archaeology. But the Second Temple of Jerusalem has its own missing treasure story.
In about 513 B.C.E, a replacement for Solomon's Temple was constructed by the residents of Jerusalem. It would go through numerous upgrades and expansions, the best-known of which happened on King Herod I's watch.
Like its predecessor, this Second Temple was also demolished by an outside force. A Jewish rebellion broke out in the year 66 C.E. Once the uprising had been quelled, the Romans reclaimed Jerusalem and knocked down the Second Temple in 70 C.E. All that remains standing is a portion of the Western Wall, which is now considered a sacred place and a pilgrimage site for those in the Jewish faith.
Before the temple fell, a golden, seven-branched menorah was kept inside. Seized by the Romans in 70 C.E, its current resting place hasn't been identified. Maybe the Visigoths stole it while sacking Rome in 410 C.E. Or perhaps the menorah journeyed to Carthage (present-day Tunisia.) A popular — and unverified — belief is that the Vatican's been hiding it this whole time. We may never get a definite answer.