Prominent is the opposite of Background. Background is related to Picture. you are likely to find Mountain in/at/on Picture. 
Monument is related to Grave. Grave is related to Bone. Bone is related to Mouth. 
Prominent <--Antonym--> Background <--RelatedTo--> Picture <--AtLocation-- Mountain 
Monument <--RelatedTo--> Grave <--RelatedTo--> Bone <--RelatedTo--> Mouth 