From PathfinderWiki
Estimated location of Tzaarban.

Tzaarban once served as the capital of the ancient cyclops civilisation of Ghol-Gan but now lies sunken beneath the waves of the Arcadian Ocean. At its height, during the Ghol-Gan classical era, Tzaarban is believed to have housed as many inhabitants as modern-day Sothis, but it has been abandoned for millennia. The city once stood amidst the heartland of ancient Ghol-Gan but, with Earthfall, the city and much of the debased kingdom surrounding it sank beneath the Arcadian Ocean. Tzaarban now lies submerged somewhere north-west of Tempest Cay on the ocean floor near the isles of the Shackles.12