Legend also tells that at the time the King failed to build Thang Long citadel, he had a dream about a Mother dog and her baby crossing the Red River to Thang Long, then ran to Nung mountain (now on Hoang Hoa Tham street). He considered them as signals of good luck, and decided to rebuild the citadel on the ground of Dai La citadel on Nung mountain, which is believed to be foundation of Kinh Thien Palace that remains traces to this day. (Photo: VNA)