en_tn/2ki/06/17.md

open his eyes that he may see

Elisha is asking that his servant may be able to see things that other people cannot see, namely the horses and chariots of fire that are around them. AT: "make him able to see" (See: rc://en/ta/man/translate/figs-idiom)

he saw. Behold

"he could see. What he saw was that"

Behold

The word "Behold" here shows that the servant was surprised by what he saw.

the mountain was full of horses

"the mountainside was covered with horses"

around Elisha

This refers to the city where Elisha is. AT: "around the city where Elisha was" (See: rc://en/ta/man/translate/figs-metonymy)