Mirumock Ruins is an intermediate grind-zone. Mirumock Ruins is primarally grinded for xp as it is the best zone in the game to grind xp. The money here is also very good when you are at the intermediate level. With that being said, grind either here or at Manshaums until you can grind either Aakman or Hystria.
Mirumock Ruins is located North of Grana; Grana is located South of Calpheon, the third major city in Black Desert.