Era is related to Literature. Literature is related to Great. Great is a synonym of Vast. Vast is related to Space. 
Room is etymologically related to Rural. Room is related to Window. you are likely to find Curtain in/at/on Window. 
Era <--RelatedTo--> Literature <--RelatedTo--> Great <--Synonym--> Vast <--RelatedTo--> Space 
Rural <--EtymologicallyRelatedTo-- Room <--RelatedTo--> Window <--AtLocation-- Curtain 