The city was heavily fortified during the 15th century as a result of its strategic position, and during the Chosŏn Dynasty, became a famous retreat for the aristocratic ryangban due to its fantastic scenery. The city's Yaksan, meaning medicine mountain, was well known for its beautiful azaleas; the famous modern poet Kim So-wŏl wrote one of his best-known poems on this subject. Two other mountains, Yaksan-dongdae, east of Yaksan, and Moran Hill are also famous scenic spots. Nyŏngbyŏn also houses many important relics, including the Ch'ŏnju and Soun Buddhist temples, dating from 1345 and 1684 respectively; the Ryuksung Pavilion, famous for "six scenic views" of Nyŏngbyŏn; and the Ch'ŏl'ong Castle, built to protect the city during the Ri Dynasty. The south gate of Nyŏngbyŏn, called Mannomun, is also famous.