PS: Most Impressive "Game of Thrones" Architectural Feature (Suggestions)

Which select "Game of Thrones" architectural feature(s) and/or architectural element(s) are the most impressive for their functionality and visual appeal? 

Live Poll: TBD
Poll List: https://www.imdb.com/list/ls067525788/ (pending)

QuickView List: https://www.imdb.com/list/ls067525788/copy/ (pending)