Olkarion is the home world of the Olkari, a race of literal tech wizards. 10,000 years ago, the Olkari were allies and friends with the Alteans, and it seems they managed to remain free until relatively recently, when the planet was invaded by a disgraced Galra commander and most of its people enslaved to construct a massive cube-shaped superweapon.
The planet seems to be divided in half by a ‘skirt’ of titanic mountains at its equator; on one side the Olkari technological development is readily visible, while the other half appears to have been left in a more natural wild state. Curiously, what we’ve seen of the planet so far seems to be in a perpetual state of sunset. Whether this is due to the planet’s distance from its sun (likely given that it seems to be the moon of a gas giant), its axial tilt, or their star being further along the main sequence is unknown.
At some point after the end of season 3, Olkarion becomes a hub for refugees liberated from the Galra as well as a staging ground for members of the Voltron Alliance to coordinate attacks on the Empire with each other.