the Holy of Holies in the Second Temple was empty.
2) Where is it? If you believe God:
Rev_11:19 Then, in heaven, the Temple of God was opened and the Ark of His covenant could be seen inside the Temple. Lightning flashed, thunder crashed and roared, and there was an earthquake and a terrible hailstorm.
Everybody knew already that the Ark was not in the Second Temple; it didn't need to be "revealed".
Then, in heaven, the Temple of God was opened and the Ark of His covenant could be seen inside the Temple
That's not the Ark of the Old Covenant, but the Ark of the New Covenant.