High up and Well-known

High up adverb - At a great altitude.

Well-known and high up are semantically related. in eminent topic. In some cases you can use "Well-known" instead an adjective phrase "High up", when it comes to topics like high-ranking.

Well-known adjective - Widely known.

High up and well-known are semantically related. Sometimes you can use "High up" instead an adjective phrase "Well-known".