Biophilia

Biophilia isn't a term commonly known, but it is one related to our evolutionary heritage.  The term was popularized by E.O. Wilson's book, "The Biophilia Hypothesis".  Wilson's argument is straightforward: we evolved as hunter-gatherers who were constantly surrounded by nature.  Therefore, modern humans have a natural affinity for objects of the natural world, such as plants, animals, and natural landscapes. 

This hypothesis can explain a lot of things, such as why so many people have pets.  It also gives us a clue about our landscape preferences.  Humans evolved in the African savannah, and therefore have a natural liking for this type of environment.  This explains why most parks possess open spaces with a few trees and rolling hills - just like an African savannah.  For a look at the real thing, here's a photo from Tanzia, Africa (credit to goanimal.com):