Ark of the Covenant: Placed in the Holy of Holies
Source: TTT
Exodus 26:33
And hang the veil from the clasps and place the ark of the Testimony behind the veil. So the veil will separate the Holy Place from the Most Holy Place.
Exodus 40:21
Then he brought the ark into the tabernacle, put up the veil for the screen, and shielded off the ark of the Testimony, just as the LORD had commanded him.
Hebrews 9:3, 4
Behind the second curtain was a room called the Most Holy Place, / containing the golden altar of incense and the gold-covered ark of the covenant. Inside the ark were the gold jar of manna, Aaron’s staff that had budded, and the stone tablets of the covenant.