Venus is portrayed is a divided planet - literally so, since it is split by the Flamebelt that girdles the planet along its equator. The Flamebelt is a region of fire and volcanos, and the Silicon Monster. In the northern part of the planet live the Treens, who are ruled by the Supreme Scientist, the Mekon, whose capitol is Mekonta. Emotion has been rigorously bred out of the Treens: they exist only to serve science. This frame below is from the original Venus story:
The Treen portrayed here is Sondar, who turns out to be the only "good" Treen.
Here is Sondar again, but this time drawn by Harold Johns. This is a frame from the Red Moon.
Desmond Walduck's view of a Treen from Prisoners of Space.
Right: Treen guards on a chariot - from Reign of the Robots.
Left: Nor would I wish to mess with these two [from The Ship That Lived].
Don Harley's view of Sondar, from Solid Space, and from Platinum Planet. The deathless words put into the mouth of this renegade Treen were by Eric Eden.
And, finally, two views of Sondar from Keith Watson. He drew what was almost a classic Mekon story, All Treens Must Die, but again the script lets it down at the end. A large part of the story is set in the city of Mekonta.
Also in the north lived the Atlantines, who had been taken from Earth 100,000 years ago [unfortunately, that predates modern Homo Sapiens!].They have evolved blue skins, and a bump on their forehead. Dan goes into a village in disguise: here he is about to be lynched. But in the process, his wig [which is also a translator!] falls off, revealing he has no bump on his forehead. He is then taken for the legendary Atlantine hero Kargaz, who successfully evaded the Treens, and who, in mythology, also had no bump.
And on the right are more Atlantines, with a Theron. Therons inhabited the southern half of Venus: they were peaceloving, living in floating homes, all their farming and manufacturing being automated.
President Kalon of the Therons - from the early Venus story.
Below: from Reign of the Robots - Atlantines and Therons. A very Hampson-like drawing.