Which ancient Greek city-state's council was the Gerousia?

Sparta, whose council of elders required members to be over sixty and served for life - so a state famous for physical excellence was governed by its oldest citizens. It also had two hereditary kings simultaneously, from separate royal houses, which was a deliberate check.

Almost everything popular about Sparta needs handling carefully. The society was underwritten by the helots, an enslaved population several times larger than the citizen body, held down by an annual ritual declaration of war that allowed them to be killed without religious pollution - the military system existed substantially to prevent a helot revolt. Spartan women held property and had more legal independence than Athenian women, which contemporaries found scandalous.

The mystique is largely ancient propaganda amplified by moderns. Sparta wrote almost nothing about itself, so accounts come from admiring outsiders like Xenophon and later Roman-era writers describing a Sparta that had become a tourist attraction performing its own legend. Nineteenth-century Prussian and then Nazi writers found the militarised, eugenic reading useful, and modern far-right movements still use Spartan imagery - which makes the historiography a live problem rather than an academic one.