This is the 7049th most frequent Chinese word.
登高
"登高" means "to ascend to a high place" or "to climb up high."
登高 here means 'climb high', referring to physically ascending a high place for viewing scenery.
秋日登高望远，景色壮丽。
In autumn, climbing high and looking far, the scenery is magnificent.
登高 in this sentence implies the act of climbing to higher elevation mountains or places.
他喜欢登高爬山，享受挑战的乐趣。
He enjoys climbing heights and hiking, enjoying the fun of challenges.
登高 metaphorically suggests making a prominent call or action from a position of visibility or importance.