The original home of the Platonians, abandoned millennia ago when its star went nova, sending the survivors first to ancient Earth and later to the planet they named Platonius.
Sahndara is described by Parmen in the original series episode Plato's Stepchildren. His people began a programme of selective breeding there, intended to produce a long-lived and refined race, before their star exploded as a nova and forced them to flee.
The refugees settled for a time on Earth in the age of the philosopher Plato, whose ideas they adopted as the model for their society. When Greek civilisation declined they moved on to an uninhabited world and named it Platonius, where a substance in the local food gave them powerful psychokinetic abilities.
By the time the Enterprise answers their call for medical help in 2268, only thirty-eight Platonians remain.