This is the 3750th most frequent Japanese word.
そびえ立つ
"そびえ立つ" means "to tower or stand tall."
In this sentence, 'そびえ立つ' describes the majestic image of the mountains standing high against the sky.
山々が青空にそびえ立っている。
The mountains are towering against the blue sky.
'そびえ立つ' metaphorically conveys the strength and stability of his unwavering determination, comparable to a tower.
彼の決意はそびえ立つ塔のように揺るぎない。
His determination is as unwavering as a towering tower.
Here, 'そびえ立つ' emphasizes the magnificent and imposing presence of the ancient castle.