I think that's why it's important to know the function of a preposition rather than memorize them.
The elevator went down. (down is an adverb modifying the verb went, answering the adverb question "where")
The cat went down the tree. (down is a preposition, linking the cat and tree in direction).
Prepositions tell how two words in a sentence are related in space (above, below, on, behind), time (before, after, during) or direction (toward, from, to).