It is called "The ear tree", due to the shape of its fruits. These guanacaste trees grow widely in the region of Guanacaste. I was intrigued by some pieces of fruits dropped on the path from my hotel apartment to the swimming pool, and took some pictures to show Eric our guide. Eric said "Ah, someone was not listening to my talk when I described this tree." Oh well, hearing a piece of information hardly enables one to recognize a tree one has never seen previously. But now I will always remember the guanacaste tree, which is the National tree of Costa Rica.