During her reign, Queen Seondeok built two great monuments: the Bunhwangsa pagoda (황룡사) and the Cheomseongdae astronomical observatory (첨성대). She also allied her country with the Tang Dynasty of China, saving her country from ruin.
Queen Seondeok was said to have dazzled her subjects with her ability to look into the future. According to legend, during her lifetime, she made three famous predictions, using the location of the stars in the sky and natural occurences. She first predicted, when she was still a princess, that she would become the first queen of Silla despite her father's efforts to produce a male heir. She then predicted, after seeing thousands of angry toads and frogs coming from the west, that the Baekje army would invade from the west, and immediately sent troops to capture the Baekje soldiers. She was correct, and that day, 2,000 Baekje soldiers were captured after having just crossed the border. Her final prediction correctly predicted the exact date and time of her death.