Something that is easily over looked is the scale of Glorantha.
The Sky Dome is about 12,000 km in diameter at its base, and its apex is about 6,000 km above the center of the Homeward Ocean. That means the Red Moon, which is about 40 km in diameter, hovers about 3,000 km above the Crater.
The Red Moon appears about half again larger in the sky than our terrestrial moon, as is the Sun (Yelm). Yelm has the same apparent magnitude as our own sun. Because the Red Moon is stationary, it is a point of reference for peoples – it is directly above in Glamour, it is high in the sky in Dragon Pass, but it is actually smaller than our moon, much dimmer and lower in the sky in Fonrit or Umathela.
Genertela is about 5,000 km long and about 1,770 km wide (or high). It is about 2,200 km from the southern coast of Genertela to the northern coast of Pamaltela. Travel between these continents is more comparable to the ancient trade across the Indian Ocean (although it is shorter distances) than to either the Mediterranean or the Atlantic travels.
See also
Here’s another way to think about it. Genertela is about a third larger than the area covered in any detail by Ptolemy’s Geographia. Places like the northern coast of Pamaltela, the Jrusteli Islands, Teleos, and the East Isles, are little more than names except for a few scholars and long-distance travellers (merchants, sailors, Wolf Pirates, and Argrath).
So Genertela is about the size of the world known reasonably well to the Greco-Romans. Which also makes sense – an educated person in Dragon Pass likely knows not only of Peloria, Kethaela, Prax, and Maniria, but of the existence of the Genert Wastes, Pent, Ralios, Seshnela, Fronela, and even Kralorela and Teshnos (even if their knowledge of details is nearly non-existent or wildly wrong). The further away, the sketchier their knowledge is – but you can always go to a Lhankor Mhy temple and find the Gloranthan equivalent of Geographia. The entires in Pamaltela might read little more than, “Mostly Harmless” or “Really Dangerous” though.
This means that for even an educated or well-traveled Genertelan, places like Pamaltela, the East Isles, the Jrusteli Isles, etc., will be completely wrapped in mystery. A few places might be known – merchants in Nochet certainly know of Afadjann and Kareeshtu, and perhaps some of the city states on the Umathelan coast, but what they know is from the Issaries Goldentongue cultists who deal with the markets there. Beyond that it is likely wildly inaccurate or entirely absent. Sailors and the few Fonritians in Nochet might spread wild tales of spices, monsters, and even stranger customs. The Vadeli are rumoured to be baby-eating demons, and the coastal cities of Umathela are described like something out of Clark Ashton Smith.
And those are the people who know the most. Inside the Lunar Empire, even less is known.