Abstract
This study investigates and analyzes natural traits in Gaudi's architectural designs on the assumption that the naturalism in his architectural designs has been built heavily on regional cultural background. In particular, focusing on four buildings Gaudi designed in his late years, this study distinguishes between natural traits found in ornaments and details, and natural traits as organic expression of form. This study shows, first, with regard to natural traits in ornaments and details, organic motives were applied to patterns, plastic objects, and parts of the building. Second, natural traits in organic expression of form were reflected by typifying $Catalu\tilde{n}a$ regional nature, using curved lines of organic shapes and realizing lively natural creatures. It is remarkable that Gaudi developed his architectural designs as unique magic naturalism based on his imagination. And In this century 'Regional Culture' gets more important in architectural designs. Gaudi's architectural works can be appreciated to represent very well $Catalu\tilde{n}a$ regional cultural identity by using properly its natural motives and objects.