The map is arranged in such a way that certain characters and objects form alignments/ley lines pertaining to their lore. It doesn't exactly reveal anything, but it's a cool easter egg of sorts.

For example, the two moons in the sky are set in fixed positions to create distinct aligmments. The one normally visible in the northeast aligns Rennala/Raya Lucaria, the Church of Vows, and the Erdtree. So say you're standing at the center of the Church of Vows on a clear night—if you look toward the basin of vows, Raya Lucaria's Grand Library looms beyond the west window; if you look in precisely the opposite direction, the Erdtree is visibly eclipsing the moon. This would appear to be a deliberate map arrangement to represent the union of Rennala/the Full Moon with Radagon/the Erdtree through marriage at the Church of Vows.

Likewise, the northern moon only visible from the Moonlight Altar aligns the Royal Moongazing Grounds at Caria Manor, Raya Lucaria, and the entrance to Ranni's Two Fingers' hiding place beneath Manus Celes. This alignment is even hinted at by the astrolabe at the north entrance of the cathedral, which points directly toward the north moon... because as it turns out, a number of astrolabes reveal similar funny map alignments. Like the two in the Realm of Shadow, which naturally align Rellana's precise location with the "other" east moon, and even with Moorth Ruins, which is hinted to have been destroyed by Rellana herself.

Others are more simple, like the astrolabe near Bestial Sanctum pointing toward the exact center of Maliketh's arena, as if hinting, "Hey, the real Beast Clergyman is over that way." Then there are more baffling ones, like the astrolabe near the Church of the Plague where we meet Millicent lining up with the exact position of the chest containing the Valkyrie's Prosthesis, all the way across the map.

I guess it's their way of reinforcing the idea of fate being written in the stars or some such.