It was also called Namdaemun because it was located in the south of the main gate of Hanyangdoseong during the Joseon Dynasty. It was built in 1396 (the 7th year of King Taejo's reign) and was the oldest wooden building in Seoul.

The building was rebuilt in 1448 (the 30th year of King sejong's reign), and it was discovered that there was a big construction in the 10th year of King Seongjong's reign (1479) during the dismantling and repair of the building between 1961 and 1963.

Later, on February 10, 2008, the fire at Sungnyemun destroyed the roof of the second floor of the pavilion and partially destroyed the roof of the first floor. After five years and two months of restoration work, it was completed on May 4, 2013 and opened to the public.

This gate is a two-story building with a two-story square measuring 5 bays in front space and 2 bays in side space, with a rainbow-shaped gate in the middle of the stone pillars. The roof has a trapezoidal shape when viewed from the front, which is called the Woojingak roof. The multi-layered structure, which is decorated on the upper part of the pillars to support the eaves of the roof, is not only on top of the pillars but also between the pillars, and the composition is not too severe and is well-organized, showing the characteristics of the early Joseon Dynasty.

It is said that Yangnyeongdaegun wrote the Hyeonpan, which reads "Sungnyemun," in the book "Jibong Yuseol." It is the oldest wooden structure in Seoul that shows the exact date of construction.

ᄋ Sungnyemun's fire-fighting fire(2008.2.10)

- The 2008 Sungnyemun arson attack was a case in which the Sungnyemun building was burnt down from February 10 to February 11, 2008. The fire broke out around 8:40 p.m. on February 10, 2008, and the second floor of Sungnyemun collapsed around 0:40 a.m. on February 11, 2008, followed by a fire on the first floor, damaging buildings except stone pillars at 1:55 a.m., five hours after the fire.

Hunminjeongeum is a commentary written in Chinese characters and published in 1446 by a group of renowned Jiphyeonjeon (Academy of Scholarly Worthies) scholars according to a royal edict issued by King sejong (r. 1418-1450). The commentary has the same title as the original, Hunminjeongeum, given to the newly invented Korean writing system but different names, including The Explanatory Edition of the Correct Sounds for the Instruction of the People (Hunminjeongeum Haeryebon) and The Original Edition of the Correct Sounds for the Instruction of the People (Hunminjeongeum Wonbon). It is a single-volume xylographic book consisting of 33 chapters. In the book, the chapters are grouped into 3 parts wherein the first part contains the main text of Hunminjeongeum in 4 chapters printed on 7 pages, each containing 7 lines of text with 11 characters per line; the second part contains a commentary in 26 chapters on 51 pages, each containing 8 lines of text with 13 characters per line. The third part contains a 3-chapter introduction of the writing system written by Jeong In-ji (1396-1478) and which ends with a date, suggesting that the Korean writing system was promulgated in 1446. According to The Veritable Records of King sejong (sejong Sillok), the Korean alphabet called Hunminjeongeum was invented in 1443 by King sejong himself and proclaimed in 1446. The commentary and Jeong In-ji’s introduction as contained in this book provide information on the scholar-statesman’s active participation in the creation of the alphabet and the basic principles used for it.

King sejong was born on May 15, 1397 in Hansungbu Junsubang (now located in Tongin-dong, Seoul) as the third son of King Taejong, the third King of the Joseon Dynasty, and became the fourth King of the Joseon Dynasty in 1418, when he was 22 years old.

King sejong made many achievements during his reign of 31 years and six months until his death at the age of 54. In 1420 (the 2nd year of King sejong's reign), Jiphyeonjeon Hall was established to cultivate promising talents and to promote learning to maintain the rituals and systems underlying Confucian politics.

The creation of Hunminjeongeum, the greatest achievement of the time, was also a result of King sejong's desire to communicate with the people.

Through the fusion of Confucian politics and independent culture, it brought great prosperity to politics, economy, society and culture during the Joseon Dynasty.

Teacher's Day is a day made to thank teachers for their hard work and is enacted and implemented in various countries, and every year October 5th is celebrated as World Teachers'' Day.

In Korea, Teacher's Day was established on May 15 in time for King sejong's Gregorian birthday from 1965.

The government will reward education contributors at the ceremony on Teacher's Day, and the winners will be given opportunities to inspect domestic and foreign industries.

In addition, various school alumni associations, women's organizations, and social organizations voluntarily offer private banKing services, especially by launching a "Finding Old Teachers" campaign to thank their teachers for their grace and deepen their priestly relations, while finding and comforting those who are suffering from illness and living difficulties among retired teachers.

The seniors and juniors and students hold a "Night of Grace" with their old teacher and teacher to thank their teacher for his grace, and attach carnations to his teacher. In addition, special lectures, sit-ins, and tea parties on the role of teachers will be held.

'Invention Day' is a day defined to promote the progress of technology by promoting invention ideas, and is May 19 every year.

This was established in 1957 to commemorate the day King sejong officially began using the rain gauge on May 19, 1442, after Jang Yeong-sil invented the world's first rain gauge in 1441, 23 (the year of King sejong's reign).

In March 1973, the day of invention was merged into the day of the sky under the regulations on various anniversaries, etc., but was revived in 1982 when the Korean Patent Association expanded and reorganized into the Korea Invention Patent Association.

Meanwhile, the rain gauge invented during the Joseon Dynasty was made with the need for a more scientific method to prepare for drought and flooding for agriculture.

It consists of a steel cylinder with a depth of 241 cm and a diameter of 16 cm, and a rain basin made of stone. The water collected in the barrel was measured with casts.

In particular, the rain gauge of Joseon was about 200 years ahead of the one invented by Italy's B. Gattelli in 1639.

Gwanghwamun is the main gate to the south of Gyeongbokgung Palace. It means "the great virtue of wages reflects the whole country."

Built in 1395, a pair of hatch sculptures are located on both sides of Gwanghwamun, a two-story pavilion. There are three Hongyemun (Archimun) on the stone pillars of Gwanghwamun. The middle door was the King's, and the other left and right doors were the servants' doors.

On the ceiling of the gate in the middle of Gwanghwamun, there is an abacus. Gwanghwamun was destroyed twice by the Korean War, and on August 15, 2010, some restoration works were completed except for Woldae and Haitai.

In modern times, the name "Gwanghwamun" itself is not only used as a castle gate, but also as a common name for sejong-ro in Beopjeong-dong, including sejong-daero and Gwanghwamun Square.

In fact, the sejong-daero intersection, where sejong-daero, Jongno-gu and Saemunan-ro intersect, is about 600 to 700 meters away from Gwanghwamun, but it is often called "Gwanghwamun intersection (intersection)".

The Uijeongbu and Yukjo government offices were established to perform key administrative functions since the Joseon Dynasty, and this area is one of the places where Seoul's history is implied along with Sungnyemun Gate.

In other words, it is one of the landmarks in Seoul.

In Korea, the day King sejong proclaimed Hunminjeongeum as Hangeul Day on October 9, and the national flag was raised as a national holiday.

On October 9 every year, Hangeul Day celebrations are held and various events are held throughout the country to renew the awareness of Hangeul and to honor the high meaning of King sejong who spread it.

sejong the Great Memorial Hall is a memorial hall located in Cheongnyangri-dong, Dongdaemun-gu, Seoul, and was built to celebrate the success and achievements of sejong the Great and to preserve it for a long time.

The sejong Daiou Memorial Business Association was laid down on October 9, 1968, completed on November 19, 1970, and opened on October 9, 1973.

It consists of exhibition rooms such as sejong the Great's one's life story room, Hangul room, science room, and Korean traditional music room.