The castle of Keretaria
Keretaria is one of Oz's small kingdoms, a city-state located in north-eastern Munchkin Country, not far from the border with Gillikin Country. It appears in Ruth Plumly Thompson's Handy Mandy in Oz.
History
When Handy Mandy lands in Keretaria, she first sees the great castle made of blue marble, and learns that it is ruled by King Kerr, with the aid of the Royal Persuader, the High Qui-Questioner, and Lord High Upper Dupper of the Realm. Kerr's nephew, the young Kerry, is the rightful ruler, but went missing two years prior.
For a thousand years a prophecy has been etched into the west wall of the castle, reading "So long as the Royal Ox of Keretaria is in good health and spirits, so long and no longer shall the present King rule over the Land." Every time harm has befallen the royal Ox, the king has been destroyed soon after. For this reason, Nox the Royal Ox is well taken care of even after Kerr usurped the throne. When Kerry was ambushed, Nox, then known as Boz, was knocked unconsious and left for dead, and when he returned to Keretaria, his horn was bent and everyone assumed he was a new ox associated with the new king.
Mandy soon learns from Himself the Elf that King Kerry is being held prisoner by the Wizard Wutz in the Silver Mountain, and sets out with Nox to rescue him. After the young king is rescued and Wutz is defeated, Kerr is revealed to have been one of Wutz's secret agents and deliberately arranged Kerry's kidnapping, and Ozma transforms him into a mole, leaving King Kerry to take back the throne. Mandy stays in Keretaria with Nox to help Kerry rule the small kingdom.
Keretaria does not appear again in the Famous Forty Oz books, but features in Nathan DeHoff's short novella The Goat Girls of Oz.