Borobudur is built as a single large stupa, and when viewed from above takes the form of a giant tantric Buddhist mandala, simultaneously representing the Buddhist cosmology and the nature of mind. Borobudur is used as a place of worship and pilgrimage. Once a year, during the full moon in May or June, Buddhists in Indonesia observe Vesak (Indonesian: Waisak) day commemorating the birth, death, and the time when Siddh?rtha Gautama attained the highest wisdom to become the Buddha Shakyamuni.