This castle in Northumberland is the stronghold of a group of humans that has survived the dragon onslaught. It is led by Quinn Abercromby and is home to many of the protagonists of the film, including Quinn, Jared, Eddie, Creedy, later Alex Jensen, and others. They have an underground bunker they take shelter in during dragon attacks, fields where they grow crops (namely tomatoes), and a large water system capable of dumping thousands of gallons of water in the castle in case it catches fire.
At some point in the ten years that pass between the male dragon's awakening and the events of the film, Quinn establishes a colony of humans in this castle. The castle serves as their home and fortress, but is later burned and destroyed by the male dragon's attack. It is presumably rebuilt after Quinn killed him. There are several dozen children that live in the castle, most of whom survive the male dragon's attack.