There are quite a few artifacts around that hint at an old occupation of the country by the desert-dwelling nithians of old: headstones covered in hieroglyphs, small pyramids, this kind of things.
One of these is a tall obelisk carved of black stone, covered in hieroglyphs that tell about these people’s journeys from there to here. It lies some distance from the road in the mountains to the northwest.
When somebody attuned to magic touches it, they can see a large stretch of greyish white, very thin sand under a black starry sky. In the distance, there is a massive grey pyramid.
What is this place? Why, the Moon, of course. What lies in the pyramid? Your guess is as good as mine.