Special traditional landmarks throughout South Korea remind the people of days past. One such landmark is the Namdaemun (South Gate). Walls used to surround Seoul, the capital, with four compass gates; Namdaemun led straight to the Deoksu Palace. Built in 1398, it still stands at in intersection in the bustling city of Seoul to remind the people of tradition. A landmark that reminds Koreans of a glorious moment in history is the Admiral Yi Sun Shin Statue located in Seoul as well. Yi Sun Shin was a naval commander that invented “turtle-ships”—the first iron-clad ships in the world. A Korean fleet of only twelve turtle-ships defeated 133 Japanese ships, preventing invasion at that time. Asia’s first night sky observatory, Chomsongdae, is also a big attraction in South Korea. It was constructed in 632 A.D. and is one of the world’s oldest observatories. There are thirty layers from bottom to top, one for each day of the month, twelve base stones, one for each month of the year, and built with 366 stones, one for each day of the year (so was believed by the people in that period).