おか
hill
oka
JMdict 1588920
丘(おか)hillの上(うえ)on topに登(のぼ)ろうlet's climb
Let's climb the hill
の (of) links 丘(おか) (hill) to 上(うえ) (top), building the place phrase “the top of the hill”. に (to) then marks that spot as the destination you’re heading toward. 登ろう(のぼろう) (let's climb) is the volitional form of 登る(のぼる) (climb) — a casual “let’s do it” suggestion.