Hebrews 12:22 says believers have come to which mountain, the city of the living God?

Answer: Mount Zion

Not to a mountain of fire and gloom, but to Mount Zion, the city of the living God, the heavenly Jerusalem.

“Instead, you have come to Mount Zion, to the city of the living God, the heavenly Jerusalem. You have come to myriads of angels”— Hebrews 12:22 (BSB)