Question: What was the capital of the Kingdom to which George Khevenhüller build a city-fortress? 
Sentence (from "Castles in Great Britain and Ireland"): David I invited Anglo-Norman lords into Scotland in the early 12th century to help him colonise and control areas of his kingdom such as Galloway; the new lords brought castle technologies with them and wooden castles began to be established over the south of the kingdom.
Relevant evidence: No