From the World Heritage inscription:
Thomas Jefferson (1743–1826), author of the American Declaration of Independence and third president of the United States, was also a talented architect of neoclassical buildings. He designed Monticello (1769–1809), his plantation home, and his ideal ‘academical village’ (1817–26), which is still the heart of the University of Virginia. Jefferson’s use of an architectural vocabulary based upon classical antiquity symbolizes both the aspirations of the new American republic as the inheritor of European tradition and the cultural experimentation that could be expected as the country matured.
While not the oddest of World Heritage Sites I’ve visited, I’m surprised that it was included for architectural reasons, not historical ones. I’m sure there are many other American buildings from the same time period which are more architecturally significant, but weren’t designed by a former president. It sort of shows you the thinking of the UNESCO committees which pick world heritage sites.
View my complete list of UNESCO World Heritage Sites