Pyramids!

All of that stuff is just to make the map a little less bland, those are all objects in maps. And those are SAND DUNES.You are over inspecting the map.
And I do guess they could add something below there, but they would need to expand the map to include the new region or extension to the nihal desert region.

Look in El Nath Mts. map,theres a sign :
"To Aqua Road<<<<"

Thats what I mean:

"To Herb Town >>"

A sign like that and zooming out the red area