In Exodus 25:22
There I will meet with you; and from above the atoning cover, from between the two cherubim which are upon the ark of the testimony, I will speak to you about every commandment that I will give you for the sons of Israel.
and in Numbers 7:89 (NASB)
Now when Moses entered the tent of meeting to speak with Him, he heard the voice speaking to him from above the atoning cover that was on the ark of the testimony, from between the two cherubim; so He spoke to him.
Can Moses enter the holy of holies?