Vast is a synonym of Great. Great is related to Very. Very is related to Narrow. 
Opening is related to Hole. you are likely to find Hole in/at/on Wall. Course is part of Wall. Course is related to Slope. 
Vast <--Synonym--> Great <--RelatedTo--> Very <--RelatedTo--> Narrow 
Opening <--RelatedTo--> Hole --AtLocation--> Wall <--PartOf-- Course <--RelatedTo--> Slope 