This location does not feature in either ChernarusPlus or Enoch (Livonia Terrain) and is only referenced by in-game maps, road signs and items.
Novigrad is the capital city of Chernarus, located on the south-west coast of the country in the Burnaya River delta. The name of the city is likely derived from the Serbian words for "new" (Нови) and "city" (град). Novigrad is only mentioned through the in-game maps seen throughout Chernarus+ and ArmA II, and is not within the playable area of South Zagoria.
Although most information about this location can only be speculated, it likely more developed compared to South Zagoria, considering that the latter is hinted as being a more remote area of the country. It is unknown whether or not Novigrad has succumbed to the Infected like South Zagoria has.