The Temple of King Solomon with the Holy of Holies at the top would be my guess.
Cooper (in his book about the Rosslyn Chapel) says that “Some have argued that this panel shows a ground plan of KST and that this is the same as the ground plan of Rosslyn Chapel.”
Oddly, this remark is followed by stating that the above: “depicts the Tabernacle in the wilderness, not KST. This can be stated with certainty as it is surrounded by the tents of the 12 tribes of Israel.” This seems a better suggestion than my own. Interestingly, if this is true, this panel might fit in the story depicted by the maps on the sides as the ‘Tabernacle in the wilderness’ is part of the Exodus story.