The fictitious 'Kingdom of Merania' was created through multiple shooting locations in Romania. Exteriors of Merania's castle were filmed at Corvin Castle in Hunedoara County (Transylvania) and the Cantacuzino Castle in Prahova County, while interiors were filmed at Bucharest's Cantacuzino Palace and the Castel Film Studios.
While the 'Kingdom of Merania' is an invention by the writers, the main shooting location Romania really used to be a kingdom. The Kingdom of Romania was a constitutional monarchy which existed from 1881, when Prince Carol I of Romania was proclaimed King, until 1947, when King Michael I of Romania abdicated and the Parliament proclaimed Romania a republic.