The idea of preserving sites that needed to be saved for the good of all humanity was born in the 1950s. At that time, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) took on the task of preserving Egypt’s Abu Simbel temples, which were in danger of being destroyed by the construction of a dam. UNESCO launched a worldwide campaign that saved the temples by relocating them to higher ground. The seed-notion of creating a list of similarly important planetary treasures was planted at this time. Read here.
https://whc.unesco.org/en/list/
https://www.worldheritagesite.org/list